My laboratory studies the structures of membrane proteins that are important in maintaining homeostasis in the brain. Understanding structure (and hence function) requires scientists to build an atomic resolution map of every atom in the protein of interest, that is, an atomic structural model of the protein of interest captured in various functional states. In 2013 we unveiled the method Microcrystal Electron Diffraction (MicroED) and demonstrated that it is feasible to determine high-resolution protein structures by electron crystallography of three-dimensional crystals in an electron cryo-microscope (CryoEM). The CryoEM is used in diffraction mode for structural analysis of proteins of interest using vanishingly small crystals. The crystals are often a billion times smaller in volume than what is normally used for other structural biology methods like x-ray crystallography. In this seminar I will describe the basics of this method, from concept to data collection, analysis and structure determination, and illustrate how samples that were previously unattainable can now be studied by MicroED. I will conclude by highlighting how this new method is helping us discover and design new drugs; shedding new light on chemical synthesis and small molecule chemistry; and showing us unprecedented level of details with important membrane proteins such as ion channels and G-protein coupled receptors (GPCRs).

Rechargeable lithium ion batteries, because of their high energy density, have conquered most of today’s portable electronics. The development of electric transportation also largely relies on the development of such devices. Still, there is plenty of room for improvement since the energy density is far from being enough for long-driving distances. The same applies for the sister technology, Na-ion, which could become the technology of choice for stationary storage in a near future. For all these applications, finding new electrode materials and being able to follow their structural evolution on charge and discharge is essential. In this talk, I will first present the strategy we use at the lab “Chimie du Solide et Energie” at Collège de France (Paris) to get useful information from diffraction experiments on battery materials, and how important a rigorous analysis of these data is for a reliable characterization of electrodes materials. From examples based on neutron and X-ray powder diffraction, I will highlight the importance of conducting structural studies, both to understand the as-made electrodes and their behaviour on cycling. Importance of crystallography and diffraction experiments will also be highlighted in the field of ionic conductors, as an important step towards the development of safe all-solid-state batteries. Lastly, it will be shown that other communities – e.g. solid state physicists- may benefit from research in materials for batteries with the discovery of compounds presenting interesting magnetic properties.

Electron density has been a great source of insight in the understanding of bonding and structure. Nonetheless, it lacks a fundamental characteristic: its connection to molecular and solid properties is barely predictive. This is so due to the lack of a direct (known) link between electron density and energetics.

Along this contribution we will try to fill this gap for several relevant cases in crystallography.

One way to approach this gap is to build energy models relying on topology. We have explored using a potential energy surface that includes chemical quantities explicitly, so that properties provided are directly related to the inherent organization of electrons within the regions provided by topological analysis [1]. Coupling this to conceptual DFT, the band gap of solids can be univocally defined [2]. Applied to zinc-blende solids as a model case, trends in band gap can be predicted in terms of bond properties (length, charge, crystalline structure- Figure 1).

Another field where energetic estimates from the electron density are missing is molecular crystals. This kind of approach would reveal extremely useful to predict the stability of different molecular crystal polymorphs or even cocrystals. In order to build this knowledge, we rely on the Non Covalent Interactions (NCI) index, which is able to identify the regions relevant to weak interactions from the electron density alone [3]. Simple approaches for well-known intermolecular energies datasets have allowed us to show that the energy can be predicted from these electron density regions using machine learning approaches in a fast and accurate manner [4]…next step is crystals!

[1] R. F. Borkman, R. G. Parr (1968) J. Chem. Phys. 48, 1116.

[2] J. Contreras-García, C. Cárdenas (2017) J Mol Mod 23, 271.

[3] E. R. Johnson, S. Keinan, P. Mori-Sanchez, J. Contreras-García, A. J. Cohen, and W. Yang, (2010) J. Am. Chem. Soc. 132 , 6498.

[4] F. Peccati, E. Desmedt, J. Contreras-García (2019) Comp. Theo. Chem., 1159, 23.

My laboratory studies how molecules on the surface of prokaryotic cells mediate cellular interaction with the environment, enabling cellular motility, initiating cellular adhesion to surfaces, and facilitating biofilm formation. For our work, we leverage our expertise in electron cryotomography (cryo-ET) in situ imaging, together with ongoing method development in subtomogram averaging approaches for structure determination of macromolecules in their native context. We combine cryo-EM with FIB milling of specimens and cryo-light microscopy to study molecules on prokaryotic cells.

In sarcomeres, α-actinin crosslinks actin filaments and anchors them to the Z-disk. FATZ proteins interact with α-actinin and five other core Z-disk proteins, contributing to myofibril assembly and maintenance as a protein interaction hub.
Here we report the first structure and its cellular validation of α-actinin-2 in complex with a Z-disk partner, FATZ-1, which is best described as a conformational ensemble. We show that FATZ-1 forms a tight fuzzy complex with α-actinin-2 and propose a molecular interaction mechanism via main molecular recognition elements and secondary binding sites. The obtained integrative model reveals a polar architecture of the complex which, in combination with FATZ-1 multivalent scaffold function, might organise interaction partners and stabilise α-actinin-2 preferential orientation in the Z-disk.
Finally, we uncover FATZ-1 ability to phase-separate and form biomolecular condensates with α-actinin-2, raising the intriguing question whether FATZ proteins can create an interaction hub for Z-disk proteins through membrane-less compartmentalization during myofibrillogenesis.

Bacterial RNA polymerase (RNAP) is an essential multisubunit enzyme performing transcription. Regulation of this process is secured through the stage-dependent interactions of RNAP with different factors (mostly proteins). Here we report the structure-function analysis of the functional complexes between RNAP and a unique helicase-like factor HelD [1] which is present in many Gram-positive bacteria (e.g. Bacillus subtilis and Mycobacterium smegmatis) [2, 3]. HelD forms tightly bound complexes with RNAP. It simultaneously penetrates into RNAP primary and secondary channels which are responsible for nucleic acids binding and substrate delivery. HelD can also interact with the RNAP active site. Structurally, these interactions are incompatible with the binding of DNA to the RNAP core and thus with the elongation stage of transcription. This is in accordance to our functional data showing that HelD is capable of clearing RNAP of nucleic acids and that HelD can dismantle RNAP-DNA complexes. HelD itself is composed of several domains, showing structural changes in solution [2] as well as in complexes with RNAP (three different structural states obtained from the cryo-EM analysis) [3]. Although we were able to link the observed dynamic behaviour with the DNA-clearing role of HelD, the recycling of HelD-bound RNAP and subsequent restart of transcription remains to be explained.

HelD as well as its complexes with RNAP resisted our attempts to crystallize them for many years. In order to get to the structural details we took the advantage of recent developments in the field of single-particle cryo-EM and were able to obtain ~3Å resolution structures. The structure of HelD itself was completely unknown with no homologue in the PDB. We combined X-ray crystallography (structure of one domain) and cryo-EM, together with bioinformatics and homologous modelling and successfully built de novo a complete atomic model of the HelD protein. For the analysis of condition-dependent dynamic behaviour we used small-angle X-ray scattering [2]. Results from our structural studies were supplemented with biochemical and biophysical assays (enzymology, analysis of interactions and stability) and by computational analyses [3].

[1] Wiedermannová, J., Sudzinová, P., Kovaľ, T., Rabatinová, A., Šanderova, H., Ramaniuk, O., Rittich, Š. & Dohnálek, J. (2014). Nucleic Acids Res. 42, 5151-5163.

[2] Kovaľ, T., Sudzinová, P., Perháčová, T., Trundová, M., Skálová, T., Fejfarová, K., Šanderová, H., Krásný, L., Dušková, J. & Dohnálek, J. (2019). FEBS Lett. 593, 996-1005.

[3] Kouba, T., Koval', T., Sudzinová, P., Pospíšil, J., Brezovská, B., Hnilicová, J., Šanderová, H., Janoušková, M., Šiková, M., Halada, P., Sýkora, M., Barvík, I., Nováček, J., Trundová, M., Dušková, J., Skálová, T., Chon, U., Murakami, K.S., Dohnálek, J. & Krásný, L. (2020). Nat Commun.11, 6419.

This work was supported by MEYS (LM2015043 and CZ.1.05/1.1.00/02.0109), CSF (20-12109S and 20-07473S), NIH (grant R35 GM131860), AS CR (86652036), ERDF (CZ.02.1.01/0.0/0.0/16_013/0001776 and CZ.02.1.01/0.0/0.0/15_003/0000447), EMBL (EI3POD) and Marie Skłodowska-Curie grant (664726).

Anomalous small-angle X-ray scattering (ASAXS) utilizes the changes of the scattering patterns emerging due to the variation of the scattering amplitude of a particular atom type upon changing the X-ray wavelength in the vicinity of the absorption edge of the atom. ASAXS on biological macromolecules is challenging due to the weak anomalous scattering effect. Biological macromolecules are also prone to radiation damage and often only available in small quantities, which further complicates the ASAXS measurements. First biological ASAXS experiments were done in the early 80-s at the European Molecular Biology Laboratory (EMBL) beamlines of the synchrotron DESY in Hamburg on metallo-proteins [1] but overall, ASAXS was not widely used in biological studies.

Recent progress in synchrotron instrumentation and dramatic increase of the brilliance of modern synchrotron sources revitalized the interest to biological ASAXS. The biological SAXS beamline P12 operated by EMBL at PETRA III storage ring (DESY, Hamburg) is dedicated to study macromolecular solutions [2] and allows for ASAXS on macromolecular solutions. The beamline was adapted to accommodate the needs for ASAXS by implementing careful data collection and reduction procedures and we report the recent developments at P12 allowing to conduct ASAXS on different macromolecular systems. Examples of utilizing ASAXS on various systems including, in particular, surfactants, nanoparticles, polymers and metal-loaded proteins are presented. The beamline control, data acquisition and data reduction pipeline developed for ASAXS on P12 are now available as standard tools for the biological SAXS community.

[1] H. B. Stuhrmann, Q. Rev. Biophys. 14, 433 (1981).

[2] C. E. Blanchet et al., J. Appl. Crystallogr. 48, 431 (2015).

Bacterial flagella are self-assembling nanomachines that enable cell motility by connecting a rotary motor to a long filament. Members of the Spirochaetes phylum, which includes important pathogens, swim using body undulations powered by the rotation of supercoiled flagella that remain confined within the periplasmic space and wrap around the cell body [1]. This behaviour diverges from that of other bacteria, where flagella function as extracellular propellers [2]. Spirochetal filaments are correspondingly distinct in composition and organization, but their molecular structure has remained elusive, obscuring the underlying mechanism for locomotion.

Here we show that, unlike all other known bacterial flagella, a highly asymmetric sheath layer coats the flagellar filament of the Leptospira spirochete and enforces filament supercoiling [3]. We solved 3D structures of wild-type and mutant flagellar filaments from L. biflexa, by integrating customized cryo-electron tomographic averaging methods with crystallographic analyses of sheath components FcpA and FcpB (Fig. 1). A central core made by FlaB (flagellin-like) protein units, delimits a central ~2nm pore.

Surrounding the core, FcpA and FcpB proteins colocalize exclusively on the outer, convex side of the filament, as an asymmetric sheath. Distinct sheath components, likely corresponding to FlaA isoforms, instead localize to the concave, inner side of the appendage. Sheath proteins were shown to produce filament supercoiling, an essential feature for flagellar-driven motility [1]. Such radial asymmetry represents a new paradigm of bacterial flagellar architecture, promoting filament supercoiling and ultimately enabling periplasmic flagella to exert their function in Leptospira translational motility. Given the large conservation of flagellar proteins across the Phylum, this asymmetric filament paradigm might prove valid for other spirochetes.

Candida albicans is the most common commensal fungus colonizing humans, and normally it does not impact the human health. However under certain conditions, it can rapidly outgrow bacterial flora causing mucocutaneous or systemic (and potentially fatal) infections. In most (mild) cases the treatment with topical and oral medications works well, however the resistant strains of C. albicans appear at the alarming pace, requiring the prompt development of new medications targeting this pathogen. One of the most promising routes to fight pathogens is to interfere with their protein synthesis machinery, therefore the structural information on ribosomes from pathogenic organisms is essential.

In this research we used an integrative structural biology approach based on the combination of single-particle cryo-Electron microscopy and macromolecular X-ray crystallography to resolve the structure of C. albicans ribosome.

We obtained 2.4 Å resolution structure of the 80S ribosome from C. albicans with the bound antibiotic and 4.2 Å resolution structure of the vacant C. albicans ribosome by single particle cryo-EM and X-ray crystallography. The comparison with other available eukaryotic ribosomes revealed unique features of C. albicans. These results can be used as a structural basis to decipher the mechanisms of antifungal resistance in C. albicans and to design novel inhibitors.

Intracellular protein crystallization occurs in many branches of life, yet the underlying cellular processes remain largely unknown. This is partly because of the scarcity of easily accessible, reproducible recombinant protein models that allow in-depth characterization of intracellular liquid-solid phase separation events. Such limitation prompts the need for identifying various classes of model proteins to examine the similarities, differences, or generalizability of such intracellular crystallization events. Furthermore, to exploit the potential values of cell-made protein crystals and the platforms to produce them, intracellular crystallization should first be understood using diverse classes of model proteins. After validating the individual crystallization events of cellular and viral proteins that readily crystallize in the ER, cytosol or nucleus, I demonstrate up to four independent crystallization events can take place concurrently in various combinations in different subcellular compartments of a single cell. For instance, by co-expressing NEU1 and human IgGs that undergo crystallization or liquid-liquid phase separation in the ER, I demonstrate two independent phase separation events can be simultaneously induced in the same continuous space of the ER lumen without mixing or interfering each other’s phase separation behaviors. Likewise, two concurrent crystallization events can take place in the cytosol or in the nucleus without mixing or interfering each other. Intracellular protein crystallization thus can happen in a crowded physiological cellular environment and does not require high protein purity. Furthermore, I report a simple method to increase the yield of intracellular protein crystals, in terms of crystal size and numbers, by treating the cells with a topoisomerase II inhibitor that blocks cell division without preventing cell size growth. This study not only presents accessible model tools for studying intriguing intracellular protein crystallization events, but also paves a way toward establishing methods and controlling the induction, quality, size, and yield of intracellular protein crystals for high-value proteins.

The recent advances of X-ray free electron lasers (XFEL) have enabled serial femtosecond crystallography (SFX) and structure determination for complex proteins such as membrane proteins in high resolution.^1-3Importantly, time-resolved (TR) studies have emerged allowing to assess their reaction dynamics. Initial demonstrations focused on light induced reactions; however, a large class of biological macromolecules acts by reaction with specific substrates requiring fast mixing approaches for TR-studies. Microfluidic tools in combination with common liquid injectors for protein crystals allow mixing times in the millisecond to second range, which is suitable to study the dynamics of enzymatic reactions with SFX at XFELs. A large drawback for TR-SFX with substrate-initiated reactions remains the large amount of protein and crystals needed to study the time evolution of a reaction. Every time point to be assessed requires a full data set which multiplies the amount of protein crystals needed by the number of time points to be studied. This may result in unsurmountable protein sample limitations requiring hundreds of mg of protein, which are not attainable for many proteins. Microfluidics allows to tackle this issue by reducing the required amount of protein sample. We propose to inject protein crystals with segmented flow approaches, which deliver crystals to the XFEL only when it pulses. We demonstrate how protein crystals in their mother liquor can be encapsulated in droplets surrounded by an immiscible oil and how these droplets can be intersected with an XFEL using common liquid jet injection methods. We demonstrated this approach reducing the amount of sample required to solve the room temperature structure of 3-deoxy-D-manno-2-octulosonate-8-phosphate synthase (KDO8PS) at the SPB/SFX instrument at the EuXFEL.⁴ Furthermore, we demonstrated the ability to electrically trigger the crystal laden droplet release in the microfluidic droplet generator, the interfacing of this approach with miniaturized optical droplet detection and an electronic feedback mechanism to tune the droplet release at a desired frequency matching the repetition rate of a particular XFEL instrument. This approach has been recently tested at the Macromolecular Femtosecond Crystallography instrument at the Linac Coherent Light Source, where the feedback mechanism was successfully implemented. Diffraction was recorded for lysozyme and the protein KDO8PS and the ability to tune the droplet release with a desired delay to the XFEL reference signal was also achieved. This is important to optimize the synchronization with the XFEL when implemented in particular chambers and various geometrical realizations of the droplet generator in relation to the XFEL interaction spot. In follow up experiments, we will assess the amount of sample that is required to obtain a full data set for KDO8PS and couple this strategy with microfluidic mixers, which have already been integrated into the 3D-printed droplet generators. With this approach, we predict that the amount of protein required to achieve a full data set can be reduced by nearly 90 %.

References:

(1) Spence, J. C. H.; Weierstall, U.; Chapman, H. N. Reports on Progress in Physics 2012, 75.

(2) Chapman, H. N.; Fromme, P.; Barty, A., et al. Nature 2011, 470, 73-U81.

(3) Martin-Garcia, J. M.; Conrad, C. E.; Coe, J., et al. Archives of Biochemistry and Biophysics 2016, 602, 32-47.

(4) Echelmeier, A.; Villarreal, J. C.; Kim, D., et al. Nat Comm 2020, 4511.

MyD88 and MAL are Toll-like receptor (TLR) adaptors that signal to induce proinflammatory cytokine production. We previously observed that the TIR domain of MAL (MALTIR) forms filaments in vitro and induces formation of crystalline higher-order assemblies of the MyD88 TIR domain (MyD88TIR). These crystals are too small for conventional Xray crystallography, but are ideally suited to structure determination by microcrystal electron diffraction (MicroED) and serial femtosecond crystallography (SFX). Here, we present MicroED and SFX structures of the MyD88TIR assembly, which reveal a two-stranded higherorder assembly arrangement of TIR domains analogous to that seen previously for MALTIR. We demonstrate via mutagenesis that the MyD88TIR assembly interfaces are critical for TLR4 signaling in vivo, and we show that MAL promotes unidirectional assembly of MyD88TIR. Collectively, our studies provide structural and mechanistic insight into TLR signal transduction and allow a direct comparison of the MicroED and SFX¹.

¹Clabbers, M., Holmes, S. et.al. MyD88 TIR domain higher-order assembly interactions revealed by microcrystal electron diffraction and serial femtosecond crystallography, Nature Communications, accepted March 2021, DOI: 10.1038/s41467-021-22590-6

.

Recombinant protein overproduction can lead to aggregation and aberrant artefacts due to the intrinsic specificities of proteins and the requirement of physiological factors (O₂ or light-sensitivity, partners, chaperones, cofactors and post-translational modifications requirements). The Wagner’s group (MPI Bremen) has developed a native shotgun approach baptized Crystallomics (Figure) to directly explore native protein complexes from anaerobic microorganisms that contain numerous exotic cofactors (e.g. iron-sulfur cluster).^1,2 After protein extraction, the soluble proteome is fractionated through successive chromatography types and the selective process of crystallisation is used as an ultimate purification step. Since this approach targets the most abundant proteins from the soluble fraction, a significant amount of protein crystals representative of the microorganism’s metabolic landscape have been obtained. Ab initio phasing was systematically used for the X-ray structure determination of these unidentified proteins. Crystals were sorted based on their colours. Sulfur-SAD^3,4 were performed on the transparent crystals by collecting high multiplicity and multi-orientations data at low energies on X06DA at the Swiss Light Source or on BL-1A at KEK. To reduce noise and improve the accuracy of the data quality some of the protein crystals were shaped with a deep-UV laser (to decrease X-ray absorption) and diffraction experiments were performed under helium environment with the recently developed PSI JUNGFRAU detector.⁵ For coloured crystals containing their native cofactors and heavy elements, X-ray fluorescent spectra were systematically measured. SAD were then performed at the edge of the atom of interest. Protein targets were then identified either by manual sequencing in the electron density maps or by fold similarity after reconstruction of a poly-alanine model.In complement to X-ray diffraction, in cristallo UV/vis absorption spectra were recorded by using the microspectrophotometer icOS⁶ at the ESRF to further investigate the nature of the state adopted by metal/absorbing centers. This synergistic approach proved that crystallisation not only separates proteins from each other but is also a powerful tool to isolate and characterized different protein states from a mixture.

[1] Vögeli B, Engilberge S, Girard E, Riobé F, Maury O, Erb TJ, Shima S, Wagner T. (2018) Proc. Natl. Acad. Sci. U S A. 27, 3380-3385.

[2] Engilberge S., Wagner T., Santoni G., Breyton C., Shima S., Franzetti B., Riobé F., Maury O., Girard E. (2019) J. Appl. Cryst.28, 722-731.

[3] Olieric V., Weinert T., Finke A. D., Anders C., Li D., Olieric N., Borca C.N., Steinmetz M.O., Caffrey M., Jinek M., Wang M. (2016) Acta Cryst. D72, 421-429.

[4] Basu S, Olieric V, Leonarski F, Matsugaki N, Kawano Y, Takashi T, Huang CY, Yamada Y, Vera L, Olieric N, Basquin J, Wojdyla JA, Bunk O, Diederichs K, Yamamoto M, Wang M. (2019) IUCrJ. 6, 373-386.

[5] Leonarski F, Redford S, Mozzanica A, Lopez-Cuenca C, Panepucci E, Nass K, Ozerov D, Vera L, Olieric V, Buntschu D, Schneider R, Tinti G, Froejdh E, Diederichs K, Bunk O, Schmitt B, Wang M. (2018) Nat. Methods.15, 799-804.

[6] von Stetten D, Giraud T, Carpentier P, Sever F, Terrien M, Dobias F, Juers DH, Flot D, Mueller-Dieckmann C, Leonard GA, de Sanctis D and Royant A. In crystallo optical spectroscopy (icOS) as a complementary tool on the macromolecular crystallography beamlines of the ESRF. (2015) Acta Crystallogr. D, 71, 15-26.

Obtaining crystals and solving the phase problem remain major hurdles encountered by bio-crystallographers in their race to get new high-quality structures. The crystallophore, Xo4, is a family of nucleating and phasing molecules based on lanthanide complexes. Tb-Xo4 was the first molecule of this family to be described [1].

Results obtained on more than fifteen proteins will be described and will show that Tb-Xo4 is an efficient tool to promote protein crystallization. Among these results, we will show that (i) Tb-Xo4 increases the number of crystallization conditions by promoting unique ones [1,2] (ii) the crystalline forms promoted by the crystallophore bypass crystal defects often encountered by crystallographers such as low-resolution diffracting samples or crystals with twinning [3] and (iii) the crystallization reproducibility is largely improved, a particular issue in structure-based drug design.

Contrary to the dogma that crystallization can only be promoted from pure protein sample, we have shown that crystals can be obtained from enriched fractions containing several proteins [3] leading to the structure determination of a protein complex [4]. Even more unexpected, the crystallophore is able to induce crystallization directly from the protein solution, as exemplified by the crystallization of hen egg white lysozyme in water [5].

Finally, we will also present preliminary results on several crystallophore variants showing complementarity with Tb-Xo4 thus enlarging the success in defining exploitable crystallization conditions.

Altogether, crystallophore is an efficient solution for protein crystallization and structure determination in the bio-crystallographer toolbox.

[1] Engilberge, S., Riobé, F., Di Pietro, S., Lassalle, L., Coquelle, N., Arnaud, C.-A., Pitrat, D., Mulatier, J.-C., Madern, D., Breyton, C., Maury, O. & Girard, E. (2017). Chem. Sci. 8, 5909–5917.[2] Jiang, T., Roux, A., Engilberge, S., Alsalman, Z., Di Pietro, S., Franzetti, B., Riobé, F., Maury, O. & Girard, E. (2020). Crystal Growth & Design. 20, 5322–5329.[3] Engilberge, S., Wagner, T., Santoni, G., Breyton, C., Shima, S., Franzetti, B., Riobé, F., Maury, O. & Girard, E. (2019). Journal of Applied Crystallography. 52, 722–731.[4] Vögeli, B., Engilberge, S., Girard, E., Riobé, F., Maury, O., Erb, T. J., Shima, S. & Wagner, T. (2018). Proceedings of the National Academy of Sciences. 115, 3380–3385.[5] de Wijn, R., Rollet, K., Engilberge, S., McEwen, A. G., Hennig, O., Betat, H., Mörl, M., Riobé, F., Maury, O., Girard, E., Bénas, P., Lorber, B. & Sauter, C. (2020). Crystals. 10, 65.

Keywords: Crystallisation; crystallophore; nucleating agents; structure determination; phasing.

Authors acknowledge financial supports from the Fondation Maison de la Chimie, Agence Nationale de la Recherche (ANR Ln23-13-BS07-0007-01) and Region AuRA for (program Xo4-2.0).

Crystallization in hydrogels is not a frequent practice in bio-crystallography, although the benefits are multiple: prevents convection and crystal sedimentation, acts as impurity filter, etc., and have been proven to be the cheapest means to produce protein crystals of high quality similar to those obtained under microgravity conditions [1-2]. Moreover, gel grown protein crystals are excellent candidates as seeds to produce crystals of bigger size for neutron diffraction or as media for crystals delivery in serial femtosecond crystallography [3].

Hydrogel should also be considered to exert control over the nucleation and growth processes. In this work we will present our most recent studies on the influence of agarose over the nucleation and growth of protein crystals. Crystal number and size was successfully tuned in a wide range of agarose concentration while keeping constant other conditions. Using five model proteins we demonstrate that the influence of gel content is independent of the protein nature, allowing the mathematical prediction of crystals flux and size with little experimental effort. The convection free environment obtained even at low agarose concentration [4] permits the obtention of high homogeneous micro-crystals slurries (Figure 1) that could be used for serial crystallography application [3] or for the mass production of enzyme crystals for industrial application [5]. Last, we will also show how it allows to explore the phase diagram under a kinetic regime that may facilitate the growth of different polymorphs.

Figure 1. Crystal size and number are fine-tuned using agarose as non-convective media during the crystallization process. (a) Proteinase-K crystals size as a function of agarose concentration and (b) as a function of precipitant concentration at fix agarose concentration of 0.1% (w/v). Scale bar is 100 µm.

[1] Gavira, J. A., Otálora, F., González-Ramírez, L. A., Melero, E., Driessche, A. E. S. v., & García-Ruíz, J. M. (2020). Crystals, 10, 68.[2] Lorber, B.; Sauter, C.; Théobald-Dietrich, A.; Moreno, A.; Schellenberger, P.; Robert, M.C.; Capelle, B.; Sanglier, S.; Potier, N.; Giegé, R. (2009). Prog. Biophys. Mol. Biol. 101, 13.[3] Artusio, F.; Castellví, A.; Sacristán, A.; Pisano, R.; Gavira, J.A. (2020). Cryst. Growth Des., 20, 5564.[4] Garcia-Ruiz, J.M.; Novella, M.; Moreno, R.; Gavira, J.A. (2001). J. Cryst. Growth, 232, 165.[5] Fernández-Penas, R.; Verdugo-Escamilla, C.; Martínez-Rodríguez, S.; Gavira, J.A. (2021). Cryst. Growth Des., 21, 1698.

Keywords: agarose hydrogel; protein crystal nucleation, serial crystallography

Supported by project BIO2016-74875-P (MINECO), Spain co-funded by the Fondo Europeo de Desarrollo Regional (FEDER funds), European Union.

Hollow molecular structures capable of guest inclusion represent an area of raising interest and lie at the forefront of the modern supramolecular chemistry.[1,2] Originally studied in solution, this concept has been extended in the solid-state, after the pioneering work on the “crystalline sponge method” (CSM). [3] The CSM primary application has been the unambiguous structural determination via SC-XRD of a single analyte encapsulated inside a porous MOF. However, as the host-guest systems often show severe disorder, their reliable crystallographic determination is very demanding [1,2] thus the dynamics of the guest entering and the formation of nanoconfined molecular aggregates has not been in the spotlight yet.

We extended the concept of the CSM stepwisely monitoring the structural evolution of nanoconfined supramolecular aggregates of guest molecules with the concomitant displacement of pristine DMF inside the cavities of a novel flexible MOF, PUM168. Furthermore, we correlated this phenomenon to the structural reorganization of the host framework, elucidating the dynamic interplay between the container and the content. [4] In order to deeply understand the “physiology” of PUM168 breathing during the guest uptake, we focused our attention on the three main actors involved in the play: i) the MOF structure, ii) the leaving DMF molecules trapped during the synthesis of the MOF and iii) the incoming guest molecules uptaken during the soaking process. [5]

The fate of each actor influences and is influenced by the other two characters, in a play that shows how the structure of the framework changes in the response of the guest positioning and composition. [5]

Interactive pores in porous coordination networks play a key role in trapping unstable species, chemical transformation, and so on . We reported porous coordination networks prepared by kinetic assembly which can be used to produce interactive pores. The interactive pore can be used for I₂ chemisorption and chemical transformation of small sulfur allotropes, from S₂ to bent-S₃ via cyclo-S₃. We performed selective formation of porous coordination networks kinetically/thermodynamically from CuI cluster and rigid T_d symmetry ligand, 4-TPPM (tetra-4-(4-pyridyl)phenylmethane), by changing cooling ratio of the hot DMSO solution of the mixture. Because the interactive pore is the key component to create functionality, it is required to extend the availability of interactive pores. Such interactive pores can be modified by changing metal source (clusters) and ligand coordination geometry. Here we report the kinetic assembly of porous coordination using Cu-Halide clusters and several pyridine-type ligands (Figure 1) to generate several interactive pore sites; we report new kinetic network formation using 4-TPPM and CuX cluster and the dynamic structural change of the kinetic network to produce highly luminescence coordination networks and flexible network formation using 3-TPPM and CuI cluster to show dual interactive sites showing iodide interactive pore sites and Cu pseudo-open metal sites.

When we performed kinetic/thermodynamic assembly using [Cu₄Br₄(PPh₃)₄] and 4-TPPM, we obtained coordination network composed of Cu₂Br₂ dimer and 4-TPPM as kinetic network and that composed of CuBr helical chain and 4-TPPM as thermodynamic network. When we heat the kinetic network at 573 K, it turned to luminescent crystalline powder. Both single crystal analysis and Rietveld refinement of PXRD indicates the transformation to the network composed of Cu⁺ connectors and 4-TPPM linkers with CuBr₂^- guests. The high quantum yield was obtained for this network (13%). We clarified that the electronic transitions in this network include TSCT in addition to the typical metal–ligand charge transfer (MLCT) observed in conventional Cu complexes. The atomic coordinates of the molecules determined from X-ray structure analysis enabled a clear understanding of the nature of the TSCT transitions.

When we performed kinetic/thermodynamic assembly using [Cu₄I₄(PPh₃)₄] and 3-TPPM, we obtained coordination network composed of Cu₂I₂ dimer and 3-TPPM as kinetic network and that composed of CuI helical chain and 3-TPPM as thermodynamic network. Using 3-TPPM, rotation motion of pyridine ring was restricted. Interestingly the thermodynamic network, CuI helical network shows 2I₂ chemisorption to make chemical bond with iodide in the interactive pore and Cu in the network so that Cu act as pseudo-open metal sites.

Iron fluoride (FeF₃.nH₂O) shows high capacity as cathode material for lithium-ion batteries combined to low toxicity and low cost. The water content of iron fluoride has been shown to be of prime importance in the performances of the cathode. So far, the various synthesis route doesn’t allow for a precise water content control, especially on the low amount regime which is the most interesting range of composition [1]. In addition, CrF₃ has been shown to increase significantly the conductivity of LiF film [2]. Consequently, it is of interest to look for the in-situ formation of the various MF_3-x(OH)_x.nH₂O phases (M = Cr, Fe).

In this contribution, we report on the in-situ formation of MF_3-x(OH)_x.nH₂O (M = Fe, Cr) phases using self-generated atmosphere. Traditionally, the heating MF₃.3H₂O in open air results in the full oxidation and decomposition of the fluorides giving rise to nano based oxides. Here, we make use of self-generated atmosphere to control the precise crystal chemistry of those phases upon heating preventing full oxidation at mild temperatures while stabilizing new phases relevant for battery applications.

Some of the results are presented in Figure 1 about the FeF_3-x(OH)_x.nH₂O phases. Precise controlled of the water content of the FeF_3-x(OH)_x.nH₂O series could be reached with n ranging from 1/3 to 0 with about 10 new pure phases. We demonstrate experimentally the initial assumption on the role played by the water in the stabilisation of the FeF₃.1/3H₂O phase, phase which is relevant for battery application [1]. In addition, the controlled in-situ decomposition of CrF₃.3H₂O led to the formation of a new CrF_3-x(OH)_x pyrochlore which was characterized structurally and magnetically. This work demonstrates the added value of in-situ experiment using self-generated atmosphere for synthetising new phases.

[1] Kim et al., (2010) Adv. Mater. 22, 5260; Ma et al. (2012), Energy Environ. Sci. 5, 8538.

[2] Tetsu O. (1984), Materials Research Bulletin 19, 451.

Investigations of long-lived reaction intermediates and metastable species generated upon external stimuli, such as light or heat, in chemical and biological systems are of upmost importance in the context of our understanding of the processes’ mechanisms and related phenomena. Linkage isomers can be formed by coordination compounds that contain ambidentate ligands capable of binding to a metal centre through various donor atoms. Such metastable species may exhibit lifetimes as long as hours or days and revert back to the ground state at elevated temperature. Thanks to their properties, photoswitchable materials may find various technological applications, including renewable energy solutions, biosensors or data storage.

The aim of this project was to thoroughly and systematically investigate conditions and dynamics of light-induced nitro group isomerisation reactions which occur in crystals of either designed or literature-reported 4th-row transition-metal complexes. The examined series of compounds consists of coordination compounds of nickel(II), copper(II) and cobalt(III). Metal centres in these systems are coordinated by the nitrite ligand and either (N,N,O) chelating species, NHC group, or amino ligands.

The studied complexes were thoroughly examined crystallographically, spectroscopically and computationally. In the case of Ni(II) and Co(III) nitro complexes partial conversion to metastable endo-nitrito isomers is achieved after irradiation of respective single crystal samples with adjusted UV-Vis LED light at temperatures above 100 K. The metastable-state form is usually stable up to relatively high temperatures, e.g. 240 K, while the maximum conversion may reach 100% for powder samples as indicated by solid-state IR measurements. Instead, copper systems analogous to the above-described nickel coordination compounds exist as the nitrito form in the ground state and work best at 10 K, whereas the metastable nitro form is usually stable only up to 60 K. Such behaviour makes them more difficult to be experimentally analysed and less applicable as functional photoactive materials.

In turn, a very significant 90% nitro-to-nitrito conversion was reported for single-crystals of the Ni(II) nitrite system [Ni(η⁵Cp)(IMes)(η¹-NO₂)]. The studied compound crystallizes with two symmetry-independent molecules comprising the asymmetric unit. Although the two moieties are geometrically very much alike, their behaviour upon irradiation or temperature appeared to be somewhat different depending on the exact experimental conditions. At 190 K the metastable species reverted back to their ground state.

Trinitrocobalt(III) coordination compounds constitute another interesting group of photoswitchable systems. For instance, Co(Me-dpt)(NO₂)₃ complex contains three different NO₂ groups in its molecule, which form different intermolecular interactions in the crystal structure, including hydrogen bonds (one is strongly bound, the second one moderately, whereas the third group does not participate in any hydrogen-bond-type contacts). After irradiating of the sample with the UV-Vis light only one of them switches to the nitrito linkage isomer, which shows the importance of crystal packing and intermolecular interactions effects.

X-ray acoustic interactions allowing to implement the control of X-ray parameters are widely studied. Among the numerous researches, it is possible to highlight the ability of controlling the spatial and energy spectrum of X-ray radiation [1] and the effect of redistribution of intensity between transmitted and diffracted beam [2]. This paper describes the implementation of a combination of these two possibilities.

Fast control of X-ray parameters, including scanning diffraction conditions and controlling by times much shorter than possibilities of traditional approaches, is a very relevant scientific task. It will be shown that overcoming of limitation of traditional approach, such as complex goniometric systems, possible by using of non-mechanical adaptive X-ray optic elements, such as X-ray acoustic resonators of longitudinal oscillations or bimorph piezo-actuators. It allows fast and precise variation of X-ray diffraction parameters, varying the angular position of the X-ray beam and controlling its wavelength. Description of schemes and elements for fast tuning of beam parameters will be given.

The effects of the redistribution of intensities between the diffracted and transmitted X-ray beams under the conditions of excitation of resonant acoustic thickness oscillations in quartz crystals were investigated. It has been established that the effect of increasing the intensity of a diffracted beam almost linearly depends on the amplitude of ultrasound (the FWHM of the rocking curves does not change at the same time) and is observed for all the studied reflexes.

The time characteristics of the observed effects upon excitation and relaxation of ultrasonic oscillations were investigated for the first time: the process of increasing intensity takes about 250 microseconds, then its oscillation is observed for about 1 millisecond, and the process of complete relaxation takes about 1.5 milliseconds.

Design of elements combining thickness and longitudinal oscillations are considered, several schemes of implementation are proposed. For the first time, the distributions of the FWHM and peak intensities of the rocking curves in a quartz resonator in case of the simultaneous excitation of longitudinal and thickness oscillations were measured. It is shown that these two types of oscillations do not have a significant mutual influence. Therefore, this combination can be used to create universal adaptive elements of x-ray optics, which allow controlling the angular position and intensity of the diffracted beam simultaneously. The effect of intensity redistribution in Potassium and Rubidium hydrogen phthalate crystals, which are emerging materials for creating a two-frequency element, was studied for the first time.

Some results and prospects of implementation of such methods and elements at synchrotron radiation as well as laboratory sources will be discussed.

[1] A.E. Blagov, M.V. Kovalchuk et al. JETP letters, t.128, 5 (11) (2005). P.893

[2] A.P. Mkrtchyan, M.A. Navasardyan, V.K. Mirzoyan. JTP letters, 8, 677 (1982)

The reported study was partially supported in the framework of the joint programs of the Russian Foundation for Basic Research (project № 18-52-05024 Arm_a and №18-32-20108 mol_a_ved) and Science Committee of Ministry of Education and Science of Armenia (project №18RF-142).

Photochromic compounds that change color reversibly by light irradiation are not only chemically interesting but are also expected to be applied to light control materials and optical storage media. So far, we have been investigating the reactivity and photochromism of salicylideneaniline derivatives and clarified that the factor that determines the photochromic characteristics is the crystal structure [1]. The cyanoalkyl cobaloxime complex crystal is a soft crystal that undergoes crystalline state photoisomerization by irradiation with visible light. This crystalline state reaction can be used to change the molecular packing, including the intermolecular interactions and the environment around the molecule, to control the reactivity of molecules in the crystal. According to this strategy, we synthesized cyanoalkyl cobaloxime complexes coordinated by photochromic compounds such as salicylideneaniline or spiropyran derivatives, which became a “dual photoreactive” complex crystal showing photoisomerization by visible light and photochromism with ultraviolet light irradiation (Fig.1). We achieved in situ control of the fading rate of these crystals by utilizing changes in the crystalline environment due to the isomerization reaction.

In this study, we synthesized three different g-cyanopropyl cobaloximes with N-(3,5-di-tert-butylsalicylidene)-3-aminopyridine(a), N-(3,5-dibromosalicylidene)-3-aminopyridine(b). and N-(5-methoxysalicylidene)-3-aminopyridine(c), and one b-cyanoethyl cobaloxime with (2-(3,3’-dimethyl-6-nitrospiro[chromene-2,2’-indolin]-l’yl)ethyl isonicotinate)(d). When the photoreactivity in the solid-state was investigated, it was confirmed that the photochromic reaction of the salicylideneaniline derivatives(a,b,c) proceeded by UV light irradiation while the photoisomerization of the g-cyanopropyl cobaloxime complex proceeded by visible light irradiation. Thus, we succeeded in obtaining a novel dual photoreactive complex crystal. After the photochromic reaction, the crystal showed colour fading to the original colour. The fading rate was found to become slower for a, c, or faster for b after the g-a isomerization reaction of the cyanopropyl group by visible light irradiation. To elucidate the fading rate change mechanism, we calculated the reaction cavity around the central part of the salicylideneaniline moiety, which would show the largest molecular shape change. For a and c, the cavity volume was reduced by the g-a isomerization, which made the movement of the atoms in the cavity more difficult, and as a result, the fading rate slowed down. In contrast, in b, the cavity volume and the fading rate increased by g-a isomerization [2]. Similarly, in the spiropyran complexes (d), we succeeded in the in situ control of the colour fading rate by visible light irradiation. For this case, the fading rate change mechanism was again rationalized by the cavity size around the spiropyran moiety [3].

Since the discovery of quasicrystals in 1982, there has been a lot of progress in finding sufficient and necessary conditions for their mathematical counterparts such as point sets and measures to have pure point diffraction. A comparatively less tackled issue is the presence of absolutely continuous components. An inherent stochasticity or randomness of the underlying structure guarantees the presence of absolutely continuous spectrum, but is not the only mechanism that does so. There are deterministic examples arising from aperiodic tilings of the d-dimensional Euclidean space which also share this feature [3,4].
In this talk, we will present the mathematical requirements for such objects to give rise to absolutely continuous diffraction components [1,5], and we will give some deterministic examples which satisfy them. We will also briefly mention several sufficient criteria to conclude the singularity of the spectrum (i.e., absence of absolutely continuous components) [1,2].

This is based on joint works with Michael Baake, Natalie Priebe Frank, Franz Gaehler and Uwe Grimm.

1. M. Baake, F. Gaehler, N. Mañibo, Renormalisation of pair correlation measures for primitive inflation rules and absence of absolutely continuous diffraction, Commun. Math. Phys. 370 (2019) 591--635.

2. M. Baake, U. Grimm, N. Mañibo, Spectral analysis of a family of binary inflation rules, Lett. Math. Phys. 108 (2018) 1783-1805.

3. L. Chan, U. Grimm, I. Short, Substitution-based structures with absolutely continuous spectrum, Indag. Math. 29 (2018) 1072-1086.

4. N. P. Frank, Substitution sequences in Z^d with a non-simple Lebesgue component in the spectrum, Ergodic Th. & Dynam. Syst. 23 (2003) 519-532.

5. N. Strungaru, On the Fourier analysis of measures with Meyer set support, J. Func. Anal. 278 (2020) 108404.

Correlated disorder in crystalline materials gives rise to single crystal diffuse scattering. While the average structure determination via Bragg data analysis is considered a standard procedure, disorder analysis is thought of as a lengthy and complicated process. We present a mean field approximation to model single crystal diffuse scattering in molecular materials from a simple pair-interaction Hamiltonian.

Mean filed theory is a self-consistent field theory, which is widely used in statistical physics to model high-dimensional random systems. It has proven a valuable tool in the analysis of magnetic diffuse scattering data [1]. Here, the formalism is applied to describe orientationally disordered molecular crystals,

We present a computational study based on the mean field model suggested by Naya [2] and proof its applicability to strongly correlated disorder, where the local building block geometry dictates allowed and prohibited local configurations. The system that will be analysed in detail is a two-dimensional analogue of Hg(NH₃)₂Cl₂ as depicted in Figure 1 (a) [3]. The Hg atoms are disordered over the cubic face centres to form [H₃N - Hg - NH₃]²⁺ molecules. The local arrangement is strictly dictated by these building rules.

We compare the results of the diffuse scattering analysis using the mean field model as introduced by Naya [2] to the results of RMC modelling and ΔPDF models based on a Warren-Cowley short range order parameter refinement (see Figure 1 (b)). Finally, the stability of the mean field analysis on limited data availability is demonstrated: Diffraction experiments under pressure or electric field yield a limited reciprocal space coverage. Here, we demonstrate the robustness of the proposed method against incomplete data sets.

Figure 1. (a) Disordered Hg(NH₃)₂Cl₂ [3], where the Hg is disordered over the cubic face centres. (b) Simulated data for a two dimensional analogue compared to refinements using mean field theory (MF), DPDF analysis for the Warren-Cowley short-range order parameters (WC) and reverse Monte Carlo modelling (RMC).

[1] Paddison, J.A.M., Stewart, J.R. et al. (2013). Phys. Rev. Letters. 110, 267207.

[2] Naya S. (1974) J. Phys. Soc. Jap. 37, 340-347.

[3] Lipscomb, W. N. (1953) Analytical Chemistry 25, 737-739.

Kossel lines and X-ray localized conical modes

V.A.Belyakov

Landau institute for Theoretical Physics, Kosygin str.2 , 119334 Moscow,

Russiabel@landau.ac.ru

An alternative way to describe the X-ray Kossel lines [1] based at the localized conical X-Ray modes existing in perfect crystals is proposed. A theory of the X-ray Kossel lines is presented in the framework of two-wave dynamical diffraction approximation for the conical modes [2]. The theoretical results compared with the known experimental results show a good general agreement with the main experimental observation as for the X-ray [3], so for the optical [4] Kossel line patterns. The influence of crucial parameters of the crystal (absorption, perfection, sample size, the Borrmann Effect etc.) on the shape of Kossel lines are discussed. For confirming a direct connection of Kossel lines with the localized conical X-Ray modes is proposed to apply a time-delayed techniques in studying the Kossel lines.

[1] Kossel, W., Loeck, V. & Voges, H. (1935). Z. Fur Phys. 94, 139.

[2] Belyakov, V. A. (2019). Diffraction Optics of Complex Structured Periodic Media, 2nd. Ed. Springer, Chapts. 5-8.

[3] Belyakov, V. A. (2021). JETP, 132, 323.

[4] Belyakov, V. A. (2020). Crystals, 132, 323.

Keywords: localized X-ray modes; Kossel line patterns; optical Kossel lines

3DED (three-dimensional electron diffraction) is currently already routinely used for the characterization of the average structure from Bragg reflections, and recently its use for quantifying correlated disorder from electron diffuse scattering is also taken off [1,2,3].

In this work, we used a combination of 3DED, HAADF-STEM and STEM-EDX to quantify the correlated disorder in Ge₄Bi₂Te₇. Ge₄Bi₂Te₇ is reported to contain vacancy-layers along <11-1>_Fm3m and <1-1-1>_Fm3m with a higher Bi-concentration neighbouring these layers, which leads to the occurrence of streaks of diffuse scattering [4, 5].

Using the combination of advanced TEM techniques, we have not only confirmed the defects previously found by single crystal X-ray Diffraction but also observed and characterized a plethora of other forms of correlated disorder not reported before in literature for this material, including domains with locally different structure and composition, interstitial atoms and local periodicity between Ge and Bi. This diversity in correlated disorder results in 3D diffuse scattering and superstructure reflections that previously passed unnoticed to other techniques.

This work illustrates the large potential of TEM in characterizing correlated disorder from the analysis of diffuse scattering.

1. Zhao, Haishuang, et al. "Elucidating structural order and disorder phenomena in mullite-type Al₄B₂O₉ by automated electron diffraction tomography." Journal of Solid State Chemistry 249 (2017): 114-123.

2. Brázda, Petr, et al. "Mapping of reciprocal space of La_{0. 30}CoO₂ in 3D: Analysis of superstructure diffractions and intergrowths with Co₃O₄." Journal of Solid State Chemistry 227 (2015): 30-34.

3. Brázda, Petr, et al. "Calcium-induced cation ordering and large resistivity decrease in Pr_{0. 3}CoO₂." Journal of Physics and Chemistry of Solids 96 (2016): 10-16.

4. Urban, Philipp, et al. "Real structure of Ge₄Bi₂Te₇: refinement on diffuse scattering data with the 3D-ΔPDF method." Journal of Applied Crystallography 48.1 (2015): 200-211. 5. Callaert, Carolien. "Characterization of defects, modulations and surface layers in topological insulators and structurally related compounds." PhD thesis, University of Antwerp, 2020.

We acknowledge the financial support of the Research Foundation-Flanders (FWO), project G035619N, “Quantification of 3D correlated disorder in materials from electron diffraction diffuse scattering with application to lithium battery materials”.

Disorder is commonly used in chemistry for designing functional materials. For instance, preparation of solid solutions is nothing else than the introduction of a controlled number of point defects in a crystal. Disordered systems, though, provide more degrees of freedom: not only the number of defects, but also their distribution can be used to optimise the functional properties of materials, however up until now, defect distribution was hard to control and thus was rarely used in practice.

In this talk we will show how to precisely tune distribution of point defects by changing various chemical parameters during crystal growth and characterise it with the single crystal diffuse scattering.

We will use Prussian Blue Analogues (PBAs) as our model system. PBAs is a class of cyanide materials with the general formula M[M’(CN)₆]_1-δ * xH₂O where M and M’ are transition metals. Depending on the nature of transition metals, PBAs can accommodate a large number of vacancies on the M’(CN)₆ site (for instance δ=0.33 for M=Mn and M’=Co) which makes them highly porous and, as a result, attractive for hydrogen storage applications. Distribution of M’(CN)₆ vacancies is important for the performance of this material, since more disordered vacancy configurations provide more diffusion pathways through the structure, larger accessible volume, and easier transport.

[1] Simonov, Arkadiy, et al. "Hidden diversity of vacancy networks in Prussian blue analogues." Nature 578.7794 (2020): 256-260.

Reverse Monte Carlo (RMC) model is a powerful tool based on supercell approach, targeting at the structure model that explains comprehensive experimental datasets. Typically, the RMCProfile package can incorporate neutron/X-ray total scattering, Bragg and extended X-ray absorption fine structure (EXAFS) data. For practical implementation, apart from theoretical pattern calculation and structure model adjustment based on metropolis algorithm, there are various effects under certain circumstances that one needs to take into account to avoid artificial effects. Here we are going to introduce several different types of correction that we recently developed and implemented, in the framework of RMCProfile, namely, 1) the correction for nano-size effect concerning total scattering modelling for nano-systems from 0D nanoparticles to 2D nanosheets [1]. 2) the implementation of arbitrary Bragg peak profile in a tabulated manner, through interacting with Topas software [2]. 3) the correction for finite instrument resolution effect going beyond the conventionally used analytical approach based on Gaussian assumption for peak shape [2]. Through such development and implementation, we hope to extend the scope of application of RMCProfile package for solving structural problems from local perspective. Typically, the implementation of resolution correction enables the modelling to an otherwise-unreachable super-large length scale, e.g., 100 Å, following the supercell approach.

The research field of magnetic frustration is dominated by triangle based lattices but exotic phenomena can also be observed in pentagonal networks. The Fe³⁺ ions in Bi₂Fe₄O₉ materialize the first analogue of a magnetic pentagonal lattice [1]. The unit cell contains two different sites of four iron atoms each, which have different connectivities with the other irons (three or four neighbours for Fe₁ and Fe₂ respectively), and that form a lattice of pentagons. Because of its odd number of bonds per elemental brick, this lattice is prone to geometric frustration. The compound magnetically orders around 240 K: the resulting spin configuration on the two sites is the same, i.e. two orthogonal pairs of antiferromagnetic spins in a plane, with a global rotation between the two sites Fe₁ and Fe_2. This peculiar magnetic structure, which is the result of the complex connectivity and magnetic frustration, has opened new perspectives in the field of magnetic frustration.

In this original compound, we have measured the spin wave excitations in the magnetically ordered state by inelastic neutron scattering. The measurements have revealed an unconventional excited state related to local precession of pairs of spins. The confrontation of the experimental results with spinwave calculations allowed to determine the Hamiltonian of the system and shows a hierarchy of the interactions. This leads to a paramagnetic state constituted of strongly coupled antiferromagnetic pairs of spins (materializing isolated dimers) separated by much less correlated spins. This produces two types of response to an applied magnetic field associated with the two nonequivalent Fe sites, as observed in the magnetization density distributions obtained using polarized neutrons.

[1] E. Ressouche, V. Simonet, B. Canals, M. Gospodinov, V. Skumryev, Phys. Rev. Lett. 103, 267204 (2009)

Crystal electric fields play an essential role in shaping the local electronic density of ions. For ions with strong spin-orbit coupling such as rare earths, this also results in defining the single-ion magnetic moment properties. Therefore, the study of crystal electric field levels is a common approach to establish the fundamental building blocks of the magnetic Hamiltonian. Indeed, the moment anisotropy and the single-ion wavefunction provide crucial information to describe complex magnetic materials such as spin liquids and multipolar systems [1,2]. In the first part of my presentation, I will illustrate this approach on the frustrated magnet SrDy₂O₄. This material exhibits two inequivalent zigzag chains of magnetic ions. The combination of low dimensionality and frustration inhibits long range order and only short range magnetic correlations are observed down to 60 mK [3]. Domain walls in the chains decay slowly and interchain interactions ultimately lead to their freezing, leading to a weakly fluctuating short range order [4]. The understanding of this complex behaviour could only be achieved from the knowledge of the moment anisotropies, established from the analysis of crystal field electric levels.

Above, we took advantage of strong spin-orbit coupling to determine magnetic properties by studying electric ones, i.e. the effect of crystal electric fields. This strong coupling between the electric charge and magnetic moment can also be used in the other direction: using magnetism to learn more about electric effects beyond the single-ion properties. As spin waves are collective excitations of the magnetic moments, the local charge densities can also sustain collective modes. Taking again the magnetic insulator SrDy₂O₄ as an example, I will demonstrate that neutron spectroscopy can measure these electric waves and that this observation is facilitated by the material’s magnetism. Interestingly, our results indicate that electric interactions dominate the magnetic interactions in this case, although they remain hidden to most measurement techniques. This observation encourages a reassessment of the description of rare-earth based magnets with unconventional properties.

[1] P. Santini, S. Carretta, G. Amoretti, R. Caciuffo, N. Magnani, G. H. Lander, Rev. Mod. Phys. 81, 807 (2009).

[2] R. Sibille, N. Gauthier, E. Lhotel, V. Porée, V. Pomjakushin, R. A. Ewings, T. G. Perring, J. Ollivier, A. Wildes, C. Ritter, T. C. Hansen, D. A. Keen, G. J. Nilsen, L. Keller, S. Petit & T. Fennell, Nat. Phys. 16, 546 (2020).

[3] A. Fennell, V. Y. Pomjakushin, A. Uldry, B. Delley, B. Prévost, A. Désilets-Benoit, A. D. Bianchi, R. I. Bewley, B. R. Hansen, T. Klimczuk, R. J. Cava & M. Kenzelmann, Phys. Rev. B 89, 224511 (2014).

[4] N. Gauthier, A. Fennell, B. Prévost, A.-C. Uldry, B. Delley, R. Sibille, A. Désilets-Benoit, H. A. Dabkowska, G. J. Nilsen, L.-P. Regnault, J. S. White, C. Niedermayer, V. Pomjakushin, A. D. Bianchi & M. Kenzelmann, Phys. Rev. B 95, 134430 (2017).

Two-dimensional (2D) materials are of intense current fundamental and applied interest as a route to create novel fundamental phenomena beyond well-established classical behaviour within their topologically constrained layers. In this context 2D monolayer graphene, formed from the isolation of weakly connected van der Waals (vdW) bonded 2D layers in graphite by exfoliation, ignited widespread interest. Exotic quantum relativistic phenomena, such as Dirac semi-metals and quantum anomalous Hall insulators, have been predicted in graphene and related materials ranging from isolated 2D monolayers to quasi-2D bulk materials with vdW bonded layers. The focus has expanded to “beyond graphene” 2D vdW layered materials with intrinsic properties such as magnetism and semiconductivity not present in graphene, however the number of materials is limited and detailed understanding only just beginning.

MnPSe₃ and CrPS₄ are such layered vdW materials that are both magnetic and semiconducting, with magnetic ions forming hexagonal and rectangular 2D motifs. To access their low dimensional behaviour we probe bulk powder and single crystal samples with neutron scattering measurements [1,2]. Through magnetic symmetry analysis and spin wave analysis we are able to isolate and explore the 2D structural and magnetic behaviour in these bulk materials. Interactions shown in Fig. 1. The data highlights subtle competing interactions in both materials that leads to the stabilization of the determined magnetic ground states. These magnetic ground states were further tuned with small applied perturbations of field and temperature and found to undergo both subtle spin alterations and more dramatic metamagnetic transitions. The determination of the intralayer and interlayer exchange interactions and anisotropy within model spin Hamiltonians allowed the underlying observed exotic bulk behaviour to be explored.

The results show that for MnPSe₃ the Se ion drives unexpectedly strong magnetic interactions between the 2D layers, which forms a contrast to the wider studies S analogue MnPS₃. While for CrPS₄ a further lowering of interaction dimensionality to 1D-chains is shown to be of significance. Collectively, these results highlight the subtle role of the crystalline structure on the emergent behaviour and show the powerful insights neutron scattering can supply to studies of low dimensional materials.

[1] S. Calder, A. Haglund, Y. Liu, D. M. Pajerowski, H. B. Cao, T. J. Williams, O. V. Garlea, D. Mandrus, “Magnetic structure and exchange interactions in the layered semiconductor CrPS₄”, Physical Review B, Phys. Rev. B 102, 024408 (2020).

[2] S. Calder, A. Haglund, A. I. Kolesnikov, D. Mandrus, “Magnetic exchange interactions in the van der Waals layered antiferromagnet MnPSe₃”, Physical Review B 103, 024414 (2021).

In the dense metal-organic framework Na[Mn(HCOO)₃], Mn²⁺ ions (S = 5/2) occupy the nodes of a ‘trillium’ net. We show that this material exhibits a variety of behaviour characteristic of geometric frustration: the Néel transition is suppressed well below the characteristic magnetic interaction strength; neutron scattering indicates that short-range magnetic order persists far above the Néel temperature; and the magnetic susceptibility exhibits a pseudo-plateau at 1/3-saturation magnetisation. We demonstrate that a simple nearest-neighbour Heisenberg antiferromagnet model accounts quantitatively for each observation, and hence Na[Mn(HCOO)₃] is the first experimental realisation of this model on the trillium net. We demonstrate how both link geometric frustration within the classical spin liquid regime to a strong magnetocaloric response at low fields.

The transverse-field Ising model on a triangular lattice is predicted to support a topological Kosterlitz-Thouless (KT) phase at nonzero temperature through a mapping of the Ising spins to a complex order parameter defined for each triangular unit. Recently, the triangular lattice antiferromagnet TmMgGaO₄ has emerged as a candidate material to realize this theoretical scenario. Through the complementary use of neutron diffraction and magnetic pair distribution function (mPDF), we have quantitatively investigated the spin correlations in TmMgGaO₄ in the temperature region of interest, tracking their evolution across the proposed transitions into and out of the KT phase. We confirm the presence of the three-sublattice order predicted for the ground state and show that the local magnetic structure undergoes distinct changes in the temperature range expected for the KT phase. Modeling the real-space mPDF reveals a preferential tendency for the system to form bound vortex-antivortex pairs, the hallmark of the KT phase, precisely in the expected temperature range. These findings constitute promising evidence for the KT phase, potentially establishing TmMgGaO₄ as a rare platform for studying KT physics in a dense spin system.

Geometrically frustrated magnets, such as triangular networks of antiferromagnetically coupled spins, can display incredibly rich physical properties that may have potential applications in quantum information science and other technologies. Determining if and how magnetic order emerges from competing magnetic tendencies is an important objective in this field. Here, we discuss the Jahn-Teller active triangular AMnO₂ (A= Na, Cu; Fig. 1) antiferromagnets [1] to highlight that the degree of frustration, mediated by residual disorder, contributes to the rather differing pathways towards a single, stable magnetic ground state, albeit with varying ordering temperatures. For these insulating sister compounds, complementary high-resolution synchrotron XRD, local-probe muon-spin relaxation (μ⁺SR) studies, corroborate that the layered NaMnO₂ adopts a remarkable magnetostructurally inhomogeneous ground state. [2] In view of this peculiarity, we employ powerful neutron total scattering and magnetic pair distribution function (PDF) analysis to uncover that although CuMnO₂ undergoes a conventional symmetry-lowering lattice distortion driven by Néel order, in the Na-derivative a short-range triclinic distortion (Fig. 2) lifts the degeneracy of the isosceles triangular network on the nanoscale, thereby enabling long-range magnetism to develop with enhanced magnetic correlations above the transition. [3] More generally, the work illuminates the cooperative intertwining of the local atomic and magnetic structures that permits ground state selection when spatial inhomogeneity meets geometrical frustration, a mechanism that may also be operative in other frustrated materials with electronically active transition metal cations.

[1] M. Giot et al., Phys. Rev. Lett. 99, 247211 (2007).

[2] A. Zorko et al., Sci. Rep. 5, 9272 (2015).

[3] B. A. Frandsen et al., Phys. Rev. B 101, 024423 (2020).

Lithium-rich transition metal oxide cathodes are of intense current interest as higher capacity alternatives to the stoichiometric layered cathodes currently used in today’s automotive applications. These Li-rich cathodes store extra energy through extensive high-voltage oxygen oxidation. The mechanism by which the changes in oxygen redox chemistry is accommodated by the cathode remains actively debated, particularly in terms of the structure changes. How does the change in O chemistry impact the structure and dynamics of the transition metal and lithium cations? Without understanding how oxygen oxidation is accommodated by the cathode structure, and how this is linked to performance limitations, we cannot design strategies to mitigate limitations and displace current automotive electrodes or develop new robust electrode chemistries that access additional O-based redox capacity.

Using operando and complementary ex situ X-ray scattering studies (XRD and SAXS) we explore the dynamic restructuring of transition metal cathodes that occurs during cycling. We identify — for the first time — the formation of nanopores within the cathode during O oxidation. Upon extended cycling, coarsening of residual pores can be linked to performance degradation

Li-ion batteries are ubiquitous in our society. However, producing high performance, safe, and sustainable batteries remains a great challenge to foster the industrial development towards e-mobility, portable and stationnary applications. Materials engineering and new chemistries are key in this objective, as well as advanced characterization tools to probe the bulk & interfacial properties of active materials. In particular, investigations in operando mode, e.g. during battery cycling under realistic conditions, are currently attracting an enormous interest. Synchrotron techniques have been widely employed to probe in real-time a large variety of battery technologies, e.g. Li-ion and beyond, to observe and map the evolving structures, in relation to materials composition & design and battery operating conditions. In this talk, we will focus on the lithiation and ageing mechanisms in advanced electrodes, and show how operando X-rays (XRD/WAXS/SAXS) experiments can provide unique insights into the structural changes in graphite [1], silicon [2] and silicon-graphite [3-4] anodes with high time/spatial resolution. In particular, spatially-resolved mXRD gives access to 2D information in the depth of the electrode, as lithiation heterogeneities and phase distributions [1], while combined SAXS/WAXS allow to determine the sequential lithiation mechanism of active phases in a composite nanostructured material [3-4]. We will also adress the challenge to build beam-compatible battery cells, which is the pre-requisite to correlate real-time microscopic information to the electrochemical performance. Last, we will introduce the novel possibilities of performing 3D quantification of structural features evolutions in complex materials.

[1] S. Tardif et al, J. Mat. Chem. A, 2021.

[2] S. Tardif et al, ACS Nano, 2017, 11, 11306–11316.

[3] C. Berhaut et al, ACS Nano, 2019, 13, 10, 11538-11551.

[4] C. Berhaut et al, Energy Storage Materials, 2020

Magnetite (Fe3O4) has emerged as a promising electrode material in rechargeable batteries because of its natural abundance, low cost, low toxicity and high specific capacities. Fe3O4 exhibits both intercalation and conversion mechanism and it involves 8 Li ions during its reduction. The multi electron transfer enables higher energy density of these electrodes compared to purely intercalation electrodes. However, it suffers from high hysteresis and high capacity loss with cycling. The reasons for the capacity fading in conversion electrodes are still not very clear and lot of research is going on with an aim to design a high capacity electrode with performance stability over a large number of cycles. In-situ/operando research in the area of batteries has gain popularity in recent past as it can give valuable information regarding changes taking place in the electrode materials during the charging-discharging of the batteries and thus can address various problems associated with battery performance [1,2].
In the present work we have used operando XAS to understand the structural changes around Fe cations during the charging-discharging of the Fe3O4 electrodes in Li ion battery. The Fe3O4 electrode has been charges and discharged at the rate of 53mAg-1 in the voltage range of 0.03-3V. The XANES data recorded during the first discharge was analysed using chemometric techniques like Principal Component Analysis (PCA) and Multivariate Curve Resolution- Alternate Least Square (MCR-ALS).
The components of the MCR-ALS analysis during the first discharge of Fe3O4 electrode have been identified respectively as Fe3O4, LixFe3O4, FeO and metallic Fe. The EXAFS analysis shows that the fraction of tetrahedral Fe cations decreases and after 0.4 electron equivalent Fe cations exists in octahedral coordination environment only. Therefore, from the operando XANES and EXAFS analysis, it becomes evident that the lithiation of magnetite during the first discharge is a multi-step process, where Li insertion in the Fe3O4 structure results in migration of Fe cations in the tetrahedral 8a site to octahedral sites (16c or 16d) and finally formation of LixFe3O4 where all Fe cations exist in octahedral coordination. The next step is conversion of LixFe3O4 phase into the rocksalt FeO phase, which finally converts to metallic Fe phase. It can also be inferred that the intercalation of Fe3O4 which results in formation of LixFe3O4, overlaps with the conversion reaction of LixFe3O4 to FeO. Further XANES and EXAFS analysis of the first charge and second discharge of Fe3O4 electrodes show that the completely lithiated electrode material never returns to Fe3O4 phase on charging, instead the subsequent cycles after the first discharge are due to the conversion reaction between FeO and metallic Fe. In conclusion, this study gives a detailed structural analysis of the Fe3O4 electrodes in Li ion battery during charging-discharging cycles.
[1] Huie, M. M., Bock, D. C., Wang, L., Marschilok, A. C., Takeuchi, K. J. & Takeuchi, E. S. (2018) J. Phys. Chem. C 122, 10316.
[2] Zhang, W., Bock, D. C., Pelliccione, C. J., Li, Y., Wu, L., Zhu, Y., Marschilok, A. C., Takeuchi, E. S., Takeuchi, K. J. & Wang, F. (2016) Adv. Energy Mater. 6, 1502471.

Recent transformations and expected growth in global energy storage and conversion systems demand developing materials [1]. Such materials in demand should be a long lasting, effective, safe, environmentally friendly, cost-effective and recyclable for use in different electrochemical applications (e.g., Lithium Sulfur Batteries, Electrochemical Capacitors, Polymer Electrolyte Membrane Fuel Cells). These requests by consumers require an innovative non-linear approach combining the materials synthesis, advanced multi-dimensional characterization techniques, real-time testing and state of art electrochemistry [2,3]. Despite efforts there are still critical challenges that have to be addressed in order to overcome intrinsic limitations and achieve both - a high energy density and a high power density [4,5]. The common denominator that the above mentioned energy storage and conversion devices share is the carbonaceous material (CM). The amount of carbonaceous material used in the electrode is approx. 30%. The CMs have different physico-chemical properties such as surface area, porosity, electronic and ionic conductivity, hydrophilicity and electrocatalytic activity. Thus, the well-tailored CM’s structural features enhance ion transport and minimize initial capacity losses even with an increase in energy density [6]. A key structural feature of carbonaceous materials together with advanced multi-dimensional characterization techniques, real-time testing and state of art electrochemistry so called operando analysis of the Lithium Sulfur Battery (LiSB) will be the subject of a presentation (Fig.1) [6,7]. The first part is related to the model-free analysis by small-angle X-ray scattering. The structural characterization of the well-tailored CMs is a crucial step towards a better understanding of the elucidation of structure-morphology-property-relationships [6]. This in turn will shed light on the processes occurring in complex energy storage and conversion systems and helps to design cost-effective, safe devices with preferably high capacities and longer lifetime over many cycles. In the second part, the simultaneous performance of several independent techniques: small-angle neutron scattering, electrochemical impedance spectroscopy, galvanostatic/potentsiostatic cycling of the LiSB test cell will be presented [7]. A nanoporous and binder-free carbon electrode was applied as a model electrode for further in situ/operando analysis, which is deemed of great importance for mechanism study of batteries. Results obtained by in situ/operando SAS techniques are scientifically interesting and technologically very relevant for next generation energy storage and conversion systems. The outline of challenges will be presented and discussed.

Compton scattering imaging is a unique technique to visualize lithiation state on electrodes of large-scale lithium-ion batteries in-situ and in-operando conditions. This technique characterized by high-energy synchrotron X-rays allows the non-destructive observation of the reaction in closed electrochemical cells and enables us to analyze quantitatively the concentration of light elements, like lithium since incoherent scattering effects are enhanced. In this study, Compton scattering imaging is applied to a 18650-type cylindrical lithium-ion cell to visualize a spatiotemporal lithiation state, called Turing pattern [1].

The Compton scattering imaging was performed at the high-energy inelastic scattering beamline BL08W of the SPring-8. The energy of the incident X-rays and the scattering angle is fixed at 115.56 keV and 90 degrees, respectively. The Compton scattered X-ray energy spectrum is measured by 9-segments Ge solid-state detector. An observation region of the cell is limited by incident and collimator slits. The size of these slits is 5 mm in height, 750 mm in width, and 500 mm in diameter, respectively. The state of charge of the sample cell was controlled using a potentiostat/galvanostat.

Figure 1 (a) shows the result of line shapes of the Compton scattering spectra, called S-parameter analysis [2], which obtained by changing the sample position along z-direction during the charging. By charging the cell, the position of each component of the cell is shifted, which is induced by intercalation/deintercalation of the lithium. Moreover, we observed S-parameter oscillations by a depth-resolved analysis of the anode and cathode. Fig. 1 (b) shows the space-time S-parameter modulation DS obtained by subtracting from S-parameter its average value in the upper cathode region. A Fourier analysis of DS shows that the dominating period of the S-parameter oscillation corresponds to the timescale of the charging curve and the dominating wavelength of the S-parameter oscillation is related to the size of the grains of the active material. The reason for the appearance of this S-parameter pattern is due to different mobilities of lithium ions and electrons and non-linear effects in the chemical reaction. Therefore, the existence of the S-parameter modulation implies that the cell can have an optimal cycle speed with a more homogeneous flow of ions.

[1] Suzuki, K., Suzuki, S., Otsuka, Y., Tsuji, N., Jalkannen, K., Koskinen, J., Hoshi, K., Honkanen, A.-P., Hafiz, H., Sakurai, Y., Kanninen, M., Huotari, S., Bansil. A., Sakurai, H. & Barbiellini, B. (2021). Appl. Phys. Lett. 118, 161902.

[2] Suzuki, K., Barbiellini, B., Orikasa, Y., Kaprzyk, S., Itou, M., Yamamoto, K., Wang, Y.J., Hafiz, H., Uchimoto, Y., Bansil, A., Sakurai, Y., & Sakurai, H. (2016). J. Appl. Phys. 119, 025103.

Over the last decades, the increased environmental pollution and vast fossil consumption generated a need for renewable energy sources. As these renewable energy sources are not always available, this also needs next-generation energy storage devices, such as lithium-ion batteries and solid oxide fuel cells. Despite the great interest in these systems, there are still gaps in the knowledge about the crystal structure evolution and phase transitions of these energy materials during the electrochemical reactions due to the submicron size of the active particles, which impede single crystal diffraction with X-rays or neutrons. Filling these gaps is crucial for understanding why a particular material functions better or worse than other closely related materials.

3D electron diffraction can be applied to submicron sized single crystals and is a powerful tool for determining the crystal structure and studying the structural changes during the electrochemical reaction [1]. However, ex situ experiments are not sufficient to solve all the questions and leave room for misinterpretation of artefacts due to, for instance, air and vacuum exposure and relaxation between cycling and structure determination and inherent differences between different crystals. Therefore, we aim to apply in situ 3D electron diffraction in a liquid filled electrochemical cell to study the crystal structure evolution upon electrochemical cycling in the transmission electron microscope.

Whereas our group was able to obtain in situ 3DED data of charged particles after a single cycle [2], in situ observation of ongoing reactions with electron diffraction has not been realized yet. One challenge is the strong scattering of the electrons by the thick liquid layer, which significantly decreases the signal-to-noise ratio [3, 4]. For obtaining data after a single cycle, this thick layer of liquid can be partially evaporated using an intense electron beam [3]. However, this procedure leaves contamination behind and prevents further cycling.

Our study aims to perform in situ 3D electron diffraction at different stages of the electrochemical process within the same experiment and therefore, without the need for evaporating part of the liquid. Our preliminary experiments on gold nanoparticles established this possibility. However, gold is an ideal system because of its high atomic number and the possibility to introduce the particles into the electrochemical cell by flushing. Studying complex and lower atomic number compounds of which the particles cannot be flushed through the cell will require optimization of the experimental conditions. Controlling all the parameters during the experiments, such as particle deposition, liquid thickness, bulging of the windows, beam irradiation and flow rate, is challenging. In this presentation, I will discuss the hurdles, the solutions and the results I have obtained so far.

[1] Hadermann J. & Abakumov A. M. (2019). Acta Cryst. B75, 485-494.

[2] Karakulina O., Demortière A., Dachraoui W., Abakumov A. M. & Hadermann J. (2018). Nano Lett. 18, 6286-6291.

[3] De Jonge N. & Ross F. M. (2011). Nature Nanotech. 6, 695-704.

[4] Tanase M., Winterstein J., Sharma R., Aksyuk V., Holland G. & Liddle J. A. (2015). Microsc Microanal. 21 (6), 1629-1638

Cellulose is our most abundant biopolymer, and hence an important renewable raw material for many materials. Her, we present a small and wide angle X-ray scattering (SAXS/WAXS) study of regenerated cellulose textile fibers, air-gap spun from an ionic liquid solution.[1] Figure 1 shows SAXS and WAXS patterns from two fibers produced with two different draw ratios, DR=2 and 15, respectively. Drawing the fibers result in an increased degree of orientation of the crystalline domains (Figure 1c and d). By analyzing the azimuthal angular dependence of the WAXS pattern, both the crystal degree of orientation and the degree of orientation of amorphous cellulose chains can be obtained, as well as their relative contributions to the total scattering. Thus, offering an accurate determination of the degree of crystallinity. The anisotropic cross-like 2D SAXS pattern, having scattering predominantly perpendicular and parallel to the fiber axis, suggests an internal colloidal structure with oriented crystalline lamellae of ca. 10 nm thickness, embedded within a continuous matrix of amorphous cellulose. The lamellae are oriented with their normal parallel with the fiber axis.

[1] Gubitosi, M., Asaadi, S., Sixta, H., Olsson, U. (2021). Cellulose. 70, 3554

Structure determination of nano-size crystals is always a challenging problem. For quite lots of materials, it is very difficult to synthesize large/good enough crystals for single crystal X-ray diffraction studies. Powder X-ray diffraction (PXRD) is the major method for their atomic structure determination, PXRD is a quite mature technique and lots of powder structures were solved. However, for complicated structures with huge unit cell dimensions or those with crystal sizes smaller than 100nm, it is quite often to have severe peak overlapping problems, which makes it extremely difficult to solve the structure from PXRD alone. Electrons which interact with matter much stronger than X-ray can produce single-crystal-like diffraction from nano-crystalline materials, which makes it possible to collect single-crystal-like diffraction data.

The 3D electron diffraction technique can be used for collecting 3D electron diffraction data. Compared with traditional electron diffraction methods, this technique gives lower dynamical effects and much higher data completeness. Using the intensities abstracted from the data, complicated structures can be directly solved using the similar methods as single-crystal X-ray diffraction. Combining it with other techniques, such as PXRD or even SXRD, more complicated structures can be solved.

A strategy to enhance surface properties of nanocrystals is tailoring their bulk crystalline structure. As an example, the performance of metal nanocatalysts is correlated to lattice distortion induced by the mechanical anisotropy of the crystal structure [1]. We demonstrated that the stress caused by interior interfaces in core@shell nanocrystals results in larger lattice deformations than the elemental lattice mismatch [2]. Plasmonic applications push further the interest for a thorough characterization of the influence of the structural anisotropy on the thermal dynamic disorder.

Here we access the thermal disorder in Pd nanocrystals with molecular dynamics simulation. We focus on cubic nanocrystals, which have a particularly pronounced influence of mechanical anisotropy. We find a marked dependence of dynamic disorder on the crystallographic direction that enhances as crystal size decreases (see Fig. 1). 10 nm nanocrystals show a clear separation of the directional-dynamic disorder profiles. Contrary to theoretical models that ignore mechanical anisotropy, the directional profiles deviate from one another starting with the shortest pair distances.

We extracted an analytical model suitable for include the anisotropic thermal disorder we report here within existing analysis methods of both Bragg and PDF powder scattering profiles. Based on experimentally validated atomistic simulations, the model is calibrated with well-known characteristic material properties such as the bulk MSD and structural mechanical anisotropy (i.e., contrast factor). Finally, we used the whole pair distribution function modelling method [3] to test the model against the analysis of powder X-ray diffraction patterns simulated via Debye scattering equation.

Cadmium selenide nanocrystals (CdSe NCs) are frequently used in optoelectronic devices, as they possess unique optoelectronic properties that are highly sensitive to their size, shape and microstructure. Due to the high sensitivity of the properties to the microstructure features, the structure and microstructure of CdSe NCs must be controlled precisely during the synthesis. The CdSe NCs crystallize in thermodynamically stable wurtzitic structure (space group ), in metastable zinc blende structure (space group ) and in a mixture of both structures [1]. As a result, another critical issue of the CdSe NCs synthesis is the control of phase composition and formation of microstructural defects, as both issues affect the optoelectronic properties additionally [2,3].

The aim of this study was to correlate the size and morphology of CdSe NCs with their phase composition and with the formation of microstructure defects, and to explain the effect of the microstructure defects on the optoelectronic properties of the CdSe NCs. The CdSe NCs under study were produced using hot injection at temperatures between 225°C and 250°C. X-ray diffraction and transmission electron microscopy with high resolution revealed that the CdSe NCs have a size between 3 and 10 nm, and crystallize predominantly in the metastable zinc blende crystal structure. While NCs having a size smaller than 4 nm were practically defect-free, larger particles contained planar defects (stacking faults), which number increased with increasing NC size. When the planar defects appeared randomly in the interior of the NCs, then they led to an anisotropic broadening of the X-ray diffraction lines as typical for isolated stacking faults [4]. When the planar defects appeared on every second cubic lattice plane {111}, then they accomplished the transition of the zinc blende structure of CdSe to the thermodynamically stable wurtzitic modification [5]. A combination of XRD measurements and simulations using DIFFaX revealed that the interplanar spacing along the stacking direction apparently depends on the density and ordering of the planar defects. Our approach is discussed together with the approach of Moscheni et al. [6].

In general, the planar defects located in the interior of the CdSe NCs deteriorate their photoluminescence quantum yield. Additional planar defects originate from the oriented attachment of CdSe NCs along the {111} crystallographic planes. These defects disturb the crystallographic coherence of attached NCs. Consequently, agglomerated NCs are not recognized as large NCs but as separated NCs both by XRD and by photoluminescence.

[1] Bawendi, M. G., Kortan, A. R., Steigerwald, M. L. & Brus, L. E. (1989). J. Chem. Phys. 91, 7282.

[2] Viswanatha, R. & Sarma, D. D. (2009). Chem.: Asian J. 4, 904.

[3] Orfield, N. J., McBride, J. R., Keene, J. D., Davis, L. M. & Rosenthal, S. J. (2015). ACS Nano 9, 831.

[4] Warren, B. E. (1990). X-ray Diffraction. New York: Dover Publication.

[5] Martin, S., Ullrich, C., Šimek, D., Martin, U. & Rafaja, D. (2011). J. Appl. Cryst. 44, 779.

[6] Moscheni, D., Bertolotti, F., Piveteau, L., Protesescu, L., Dirin, D. N., Kovalenko, M. V., Cervellino, A., Pedersen, S., Masciocchi, N. A. & Guagliardi, A. (2018). ACS Nano 12, 12558.

Understanding and governing the complex behavior in magnetic materials at the nanoscale is the key and the challenge not only for fundamental research but also to exploit them in applications ranging from catalysis,[1] to data storage,[2] sorption,[3-4] biomedicine,[5-6] and environmental remediation.[7] In this context, spinel ferrites (M²⁺Fe²O⁴, where M²⁺ = Fe, Co, Mn, etc.) represent ideal magnetic materials for tuning the magnetic properties through chemical manipulations, due to their strong dependence on the cation distribution, spin-canting, interface, size, shape, and interactions. Furthermore, when coupled with other phases (heterostructures), they can display rich and novel physical properties different from the original counterparts (exchange coupling, exchange bias, giant magneto-resistance), allowing them to multiply their potential use.[8] For example, the possibility to tune magnetic anisotropy and saturation magnetization by coupling magnetically hard and soft materials have found usage recently in applications based on magnetic heat induction, such as catalysis or magnetic fluid hyperthermia (MFH).[9] Therefore, it is crucial to engineer core-shell nanoparticles with homogeneous coating and low size dispersity for uniform magnetic response and to maximize the coupling between the hard and soft phases (i.e. the interface).[10] Even though some studies have reported interesting results in the field of magnetic heat induction, a systematic study on an appropriate number of samples for a better comprehension of the phenomena to optimize the performance is needed.

In this contribution, the capability of coupled hard-soft bi-ferrimagnetic nanoparticles to improve the heating ability is exploited to understand the influence of the different features on the performances. This systematic study is then based on the correlation between the heating abilities of three magnetically hard cobalt ferrite cores, covered with magnetically soft spinel iron oxide and manganese ferrite having different thickness, with their composition, structure, morphology and magnetic properties. Direct proof of the core-shell structure formation was provided by nanoscale chemical mapping, with identical results obtained through STEM-EELS, STEM-EDX, and STEM-EDX tomography. ⁵⁷Fe Mössbauer spectroscopy and DC/AC magnetometry proved the magnetic coupling between the hard and the soft phases, thanks also to the comparison among core-shell NPs, ad-hoc prepared mixed cobalt-manganese ferrites NPs, and cobalt ferrite NPs mechanically mixed with manganese ferrite NPs. The heating abilities of the aqueous colloidal dispersions of the three sets of core-shell samples revealed that, in all cases, core-shell nanoparticles showed better performances in comparison with the respective cores, with particular emphasis on the spinel iron oxide coated systems and the samples featuring thicker shells. This scenario entirely agrees with the hypothesis made based on magnetic parameters (saturation magnetization, Néel relaxation times, effective anisotropy) of the powdered samples, and demonstrated the importance of a sophisticated approach based on the synergy of chemical, structural, and magnetic probes down to a single-particle level.

[1] Polshettiwar, V. et al. Chem. Rev., 2011, 111, 3036–3075

[2] Wu, L. et al. Nano Lett., 2014, 14, 3395–3399

[3] Cara, C. et al. J. Mater. Chem. A, 2017, 5, 21688–21698

[4] Cara, C. et al. J. Phys. Chem. C, 2018, 122, 12231–12242

[5] Lim, E. et al. Chem. Rev., 2015. 115, 327-394

[6] Mameli, V. et al. Nanoscale, 2016, 8, 10124–10137

[7] Westerhoff, P. et al. Environ. Sci. Nano, 2016, 3, 1241–1253

[8] Gawande, M.B. et al. Chem. Soc. Rev. 2015, 44, 7540–7590

[9] Lee, J.-H. et al. Nat. Nanotechnol.,2011, 6, 418–422

[10]Sanna Angotzi, M. et al. J. Nanosci. Nanotechnol., 2019, 19, 4954–4963

Lead bromide perovskite nanocrystals (NCs) APbBr₃ in which A: Cs, FA: CH(NH₂)₂, MA: CH₃NH₃ are very promising high-color purity light emitters due to their pure green emission and excellent optical properties. In this present work, the lead bromide perovskite APbBr₃ (A: Cs, FA, MA)nanocrystals have been synthesized by the hot injection method according to. Imran et al ¹ synthesis approach in which the benzoyl bromide was used as halide precursor which can be easily injected into a solution of metal cations to provoke the nucleation and the growth of Lead bromide perovskite NCs. By precisely tuning the relative amount of cation precursors (cesium carbonate and lead acetate for Cs perovskite, formamidine acetate and lead acetate for FA perovskite, and methylamine and lead oxide for MA perovskite), ligands (oleylamine and oleic acid), solvents (octadecene), benzoyl bromide, and the injection temperature (170°C Cs perovskite, 75°C for FA perovskite, 65 °C for MA perovskite), we have been able to synthesize inorganic and organic-inorganic lead bromide perovskite APbBr₃ colloidal nanocubes with excellent control over the size distribution, very high phase purity, and excellent optical properties such as a high green photoluminescence emission efficiency and narrow full width at half-maximum. The resultant lead bromide perovskite nanocrystals (NCs) APbBr₃ present important optical properties, which are among the best-promoting characteristics for a pure green light-emitting device according to the updated recommendation 2020 (Rec. 2020) standard ².

References:

1: Imran, Muhammad, et al. "Benzoyl halides as alternative precursors for the colloidal synthesis of lead-based halide perovskite nanocrystals." Journal of the American Chemical Society 140.7 (2018): 2656-2664.

2: Zhu, Ruidong, et al. "Realizing Rec. 2020 color gamut with quantum dot displays." Optics express 23.18 (2015): 23680-23693.

X-ray powder diffraction and electron single crystal diffraction, although having very different methodologies in their cores, target the same material, and can deliver complimentary information for the structure characterization.

X-ray powder diffraction is a well-established technique; its performance can be exemplified by a number of impressive highlights [1-3]. A structure analysis with powder X-ray diffraction runs thorough three main steps – (i) indexing of the powder profile, (ii) structure solution, and (ii) structure refinement. The first step represents the bottleneck for the whole procedure, being associated with the inherent problem of the powder method – projection of all reflections onto a single axis. The most difficult cases represent polyphasic samples, large unit cell volumes, and low symmetry structures.

Electron diffraction method, being able to address nanocrystals individually, allows to collect 3D single crystal data from crystals with the size down to tens of nanometres [4]. A 3D reconstruction of the reciprocal space immediately delivers information on the unit cell metric. The inherent problems of electron diffraction appear at later stages, when quantification of reflection intensities is required. The strong interaction of electrons with matter gives rise to multiple scattering, which modifies intensities of reflections in a complex manner. Recently, methods for dynamical structure refinement became available [5]; still the multiple scattering contribution cannot be accounted for during the structure solution (model building) step.

In this light, an obvious beneficial combination of two techniques is the transfer of unit cell parameters, determined from electron diffraction to powder X-ray data for subsequent structure solution and refinement. This workflow will be demonstrated by examples. Beyond this combination, analysis of diffuse scattering by the two methods will be presented, and combined analysis of total scattering for PDF calculation will be discussed.

[1] Vella-Zarb, L., Baisch, U., Dinnebier, R. E. (2013). J. Pharm. Sci., 102, 674. [2] Schlesinger, C., Bolte, M. and Schmidt, M. U. (2019). Z. Kristallogr. 234, 257. [3] Spiliopoulou, M. Karavassili, F. Triandafillidis, D.-P. Valmas, A. Fili, S. Kosinas, C. Barlos, K. Barlos, K. K. Morin, M. Reinle-Schmitt, M. L. Gozzo F. and Margiolaki, I. (2021). Acta Cryst. A77. [4] Gemmi, M., Mugnaioli, E., Gorelik, T.E., Kolb, U., Palatinus, L., Boullay, P., Hovmöller, S., Abrahams, J.P. (2019). ACS Cent. Sci. 5, 1315. [5] Palatinus, L. Brázda, P. Jelínek, M. Hrdá J., Steciuk, G. Klementová M. (2019). Acta Cryst., B75, 512.

Unit cell determination, phase identification, structure determination, structure refinement. At one point of time, X-ray powder diffraction (XRPD) was the way to go for structure characterization of microcrystalline powders, despite the analyses sometimes being slow and tedious. For a long time, we have known that electron diffraction (ED) data from microcrystals are useful for unit cell and structure determination. We would still resolve to XRPD for structure refinement, because the data are kinematical and therefore simpler to model.
Over the last 15 years, developments in ED methodology, both hardware and software, have reached a point where high-quality data can be collected routinely on a large number of crystals [1, 2]. When of sufficient quality, structures refined against these data challenge the accuracy of what can be obtained from XRPD data. By combining data from different crystals using cluster analyses, we showed that even physically meaningful anisotropic ADPs can be obtained from ED data [3]. These are notoriously difficult to obtain from XRPD data.
What can we not do with ED? Through serial crystallography experiments, we saw that it is possible to collect ED data from hundreds or thousands of crystals automatically [2]. This opens the door for automated quantitative phase analysis using ED data [3, 4, 5], challenging the bulk information that can be obtained from XRPD data. Then what do we still need XRPD data for?

[1] M.O. Cichocka, J. Ångström, B. Wang, X. Zou, S. Smeets, J. Appl. Cryst. 51(6), 1652-1661
[2] B. Wang, X. Zou, S. Smeets, IUCrJ 6(5), 854-867
[3] S. Smeets, S. I. Zones, D. Xie, L. Palatinus, J. C. Pascual, S.-J. Hwang, J. E. Schmidt, L. B. McCusker, Angew. Chem. Int. Ed. 58(37), 13080-13086
[4] S. Smeets, J. Ångström, C. O. A. Olsson, Steel Res. Int. 90(1), 1800300
[5] Y. Luo, B. Wang, S. Smeets, J. Sun, W. Yang, and X. Zou, Manuscript in preparation.

Magadiite, Na₂Si₁₄O₂₈(OH)₂·nH₂O, is known as a mineral discovered at the lake Magadi in Kenya by Hans Eugster in 1967 [1]. Since then, magadiite-type materials have also frequently been synthesized in the lab and have come into focus for various applications [2-4], like CO₂ adsorbents, drug carriers or catalysts and maintain a rising interest.

Despite many attempts, the unique magadiite structure remained unsolved. Finally, a material-specific strategy based on 3D electron diffraction successfully deciphered the atomic structure [5]. In order to enable the ab initio structure solution of the electron beam sensitive material, a sodium-free dehydrated form of magadiite was synthetically isolated and, from that, it was subsequently possible to derive a structure model for the sodium form of magadiite, later successfully refined against powder X-ray diffraction data. Furthermore, a geometry optimization, simulations of spectroscopic data and calculation of charge transfer between the water molecules and the silicate layer with DFT methods confirmed the obtained crystal structure of sodium magadiite.

The structure of the silicate layer is quite complex, as it contains 4-, 5-, 6-, 7-, and 8-rings of three- and four-interconnected [SiO_4/2] tetrahedra. Seven symmetrically independent Si atoms and 15 independent oxygen sites are present forming a dense layer of considerable thickness (11.5 Å). The symmetry can be described by the layer group c211. Each layer is chiral, but the chirality of the stacked silicate layers in the average structure (F2dd) is alternated, due to the glide plane perpendicular to the stacking axis. Bands of interconnected [Na(H₂O)_6/1.5]⁺ octahedra are intercalated between neighbouring silicate layers to compensate the charge of the layers.

The detailed knowledge now achieved on the previously unknown silicate layer and the development of an adapted synthesis combined with an ammonia-based titration will have a huge impact on the research of hybrid organic−inorganic nanocomposites based on magadiite, related layered silicates and zeolite-like structures in order to design new and more efficient materials.

Figure 1. Number of publications mentioning magadiite. Inset illustrates the structure of sodium magadiite with view along [110].

[1] Eugster, H. P. (1967). Science. 157, 1177–1180.

[2] Ge, M., Tang, W., Du, M., Liang, G., Hu, G. & Jahangir Alam, S. M. (2019). European Journal of Pharmaceutical Sciences. 130, 44–53.

[3] Paz, G. L., Munsignatti, E. C. O. & Pastore, H. O. (2016). Journal of Molecular Catalysis A: Chemical. 422, 43–50.

[4] Vieira, R. B., Moura, P. A. S., Vilarrasa-García, E., Azevedo, D. C. S. & Pastore, H. O. (2018). Journal of CO₂ Utilization. 23, 29–41.

[5] Krysiak, Y., Maslyk, M., Silva, B. N. N., Plana-Ruiz, S., Moura, H. M., Munsignatti, E. O., Vaiss, V. S., Kolb, U., Tremel, W., Palatinus, L., Leitão, A. A., Marler, B. & Pastore, H. O. (2021). Chemistry of Materials [accepted].

This research was supported by the Czech Science Foundation (project number 19-08032S).

Polymorphism is a common aspect of most commercially relevant drugs. One-third of crystalline organic molecules and about half of marketed active pharmaceutical ingredients (APIs) are known to form polymorphs [1, 2]. The characterization of all polymorphic species and the understanding of the overall polymorphic energy landscape represents a prominent aspect of drug development and is crucial to establish efficacy, formulation and shelf life. Moreover, the discovery of new polymorphs with different chemical and physical properties may result in treatments that are more effective and with reduced side effects [3].

Here, we report the crystallization, structure determination and dissolution behaviour of the δ-polymorph of the non-steroidal anti-inflammatory drug indomethacin (IMC), a poorly studied polymorph first mentioned almost 50 years ago [4] and whose structure has remained hitherto unknown. δ-IMC shows a significantly enhanced dissolution rate compared with the more common and thoroughly studied α- and γ-polymorphs, potentially connected with an increased bioavailability.

Pure δ-IMC was obtained via desolvation of the methanol solvate form. Its crystallisation results in fibrous crystals that are too tiny for conventional single-crystal X-ray diffraction (XRD). Structure determination was therefore obtained on the basis of continuous three-dimensional electron diffraction (3D ED) [5], recorded by a single-electron detector [6]. The structural model obtained from 3D ED was refined using the Rietveld method against powder XRD data, following the protocol used for other pharmaceutical compounds [7, 8] and allowing the accurate determination of free torsion angles and intermolecular bonding.

The structure solution provides a solid clarification of δ-IMC spectroscopic IR and Raman data and a tentative interpretation for still unsolved indomethacin metastable polymorphs. Moreover, it explains the observed solid-solid transition from the δ-polymorph to the α-polymorph, which is likely driven by similarities in molecular conformation.

The applied procedure for structure determination may be implemented as a standard protocol for the R&D department of a pharmaceutical company.

[1] Hilfiker, R. (2006). Polymorphism: In the Pharmaceutical Industry. Weinheim: Wiley.

[2] Cruz-Cabeza, A. J., Reutzel-Edens, S. M. & Bernstein, J. (2015). Chem. Soc. Rev. 44, 8619.

[3] Gao, L., Liu, G., Ma, J., Wang, X., Zhou, L. & Li, X. (2012). Controlled Release 160, 418.

[4] Borka, L. (1974). Acta Pharm. Suec. 11, 295.

[5] Gemmi, M., Mugnaioli, E., Gorelik, T. E., Kolb, U., Palatinus, L., Boullay, P., Hovmöller, S. & Abrahams, J. P. (2019). ACS Cent. Sci. 5, 1315.

[6] Nederlof, I., Van Genderen, E., Li, Y. W. & Abrahams, J. P. (2013). Acta Cryst. D69, 1223.

[7] Andrusenko, I., Hamilton, V., Mugnaioli, E., Lanza, A, Hall, C., Potticary, J., Hall, S. R. & Gemmi, M. (2019). Angew. Chem. Int. Ed. 131, 11035.

[8] Andrusenko, I., Potticary, J., Hall, S. R. & Gemmi, M. (2020). Acta Cryst. B76, 1036.

We thank Diamond Light Source Synchrotron Facility for obtaining simultaneous synchrotron powder XRD and differential scanning calorimetry (DSC) data.

The crystal structure of a novel high pressure, high temperature tin oxynitride phase (Sn₂N₂O) was solved via Automated Electron Diffraction Tomography (ADT) [1]. The new phase was synthesized from a Sn-N-O precursor at 20 GPa and 1200-1500°C. Due to strong overlaps of symmetrically non-equivalent reflections, attempts to solve the unknown structure based on X-ray powder diffraction data were not successful. The use of the ADT method allows to collect three dimensional electron diffraction data (3D ED) from single nanocrystals in the TEM via a tilt movement of the crystal and sequential diffraction pattern acquisition [2]. Subsequently, the reciprocal space is reconstructed and unit cell parameters as well as space group information can be derived. The electron diffraction intensities can be extracted and used to solve the crystal structure via approaches like “direct methods”.

The new oxynitride phase crystallizes in space group Pbcn with the unit cell parameters: a=7.83 Å, b=5.53 Å, c=5.54 Å. The crystal structure could be solved ab initio with direct methods and refined taking both the kinematic and dynamic theory of scattering into account. It resembles a Rh₂S₃ type structure where the Sn atoms are sixfold coordinated by O and N atoms. The refined structure compares very well with DFT calculations demonstrating the quality of data achievable with ADT and its applicability for the structure solution of high pressure and high temperature materials.

[1]Bhat S., Wiehl L., Haseen S., Kroll P., Glazyrin K., Gollé-Leidreiter P., Kolb U., Farla R., Tseng J., Ionescu E., Katsura T. & Riedel R. (2020). Chem. Eur. J. 26, 2187-2194

[2]Kolb U., Krysiak Y. & Plana-Ruiz S. (2019). Acta Cryst. B 75, (4) 463-474.

3D electron diffraction (3D ED) has recently emerged as an alternative to x-ray diffraction to elucidate the atomic structure of nano-sized beam sensitive crystals¹. LD-EDT² is a recently developed low dose 3D ED technique for ab initio structure determination of beam sensitive crystals such as hydrated minerals or MOFs. Low dose conditions are achieved by optimizing exposure during specimen tilting. High quality diffraction data can be obtained from very small crystals without damaging the structure, and a precise sampling of the reciprocal space is assured by beam precession. We recently applied LD-EDT on Bulachite³, a hydrated Al arsenate mineral, to solve its atomic structure. Difficulties related to the small size of crystals as well as beam sensitivity due to the presence of H2O molecules inside the lattice were overcome by LD-EDT, where synchrotron x-rays previously failed. The resulting structure⁴ is comprised of layers containing edge-sharing Al-O octahedra, inter-connected with As-O tetrahedra by corner sharing. The localization of light atoms in the lattice showcases the potential of electron crystallography for yielding high quality diffraction data even under low dose conditions.

https://www.olexsys.org/

https://www.olexsys.org/

https://journals.iucr.org/j/issues/2021/03/00/in5046/

Producing sufficient amounts or stable, properly folded protein is an essential prerequisite for protein crystallization, especially for challenging targets such as membrane proteins. However many proteins in their native form show limited stability and are refractory to expression in recombinant hosts. Over the last several years, ancestral sequence reconstruction has (ASR) emerged as a useful tool by which protein engineers and crystallographers can obtain highly robust forms of proteins of interest, which are often also expressed at relatively high levels in Escherichia coli. ASR involves inferring the ancestral state from an alignment of the sequences of extant forms of a given protein family, an evolutionary tree that represents their phylogeny, and an amino acid substitution model. We have developed a suite of software (GRASP: Graphical Representation of Ancestral Sequence Predictions) which enables the inference of ancestral protein sequences from alignments of up to ~ 10000 sequences using maximum likelihood, joint or marginal reconstruction methods. GRASP has been exemplified using several families of eukaryotic cytochrome P450 enzymes, membrane-bound, haemoprotein monooxygenases that have typically been challenging to express and crystallise. To date ASR has enabled expression of ancestral eukaryotic P450s at levels up to ~ 7 µM in E. coli cultures (~350 mg/L culture) leading to the successful crystallization of representative enzymes from several P450 subfamilies. While the resurrected ancestral proteins may not be identical to the extant proteins of principal interest, crystallization of ancestral homologues can provide insights into the structure of a protein family, including how to stabilize the protein fold. In addition, ancestors provide a robust and relevant template for structure function studies as well as protein engineering. When applied to previously uncharacterized sequences, ASR could enable the discovery of new folds and accelerate the functional and structural annotation of sequence-structure-function relationships in novel protein families.

Atomic crystal structure affects the electromagnetic and thermal properties of common matter. Similarly, the nanoscale structure controls the properties of higher length-scale metamaterials, for example nanoparticle superlattices and photonic crystals. We have investigated the self-assembly and characterization of binary solids that consist of crystalline arrays of 1) spherical viruses / other protein cages and 2) functional units [1]. The extremely well defined structure of protein cages (e.g. CCMV, TMV and ferritins) facilitates the construction of co-crystals with large domain sizes. The use of a second functional unit allows highly selective pre- or post-functionalization with different types of functional units, such as organic dyes [2,3], supramolecular hosts [4] and enzymes [5].

In the case of rod-like protein assemblies (e.g. tobacco mosaic virus), well-defined binary superlattice wires can be achieved [6]. The superlattice structures are explained by a cooperative assembly pathway that proceeds in a zipper-like manner after nucleation. Curiously, the formed superstructure shows right-handed helical twisting due to the right-handed structure of the virus. This leads to structure-dependent chiral plasmonic function of the material.

Our systematic approach identifies the key parameters for the assembly process (ionic strength, electrolyte valence, pH) and highlights the effect of the size and aspect ratio of the virus particles, which ultimately control the crystal structure and lattice constant. Protein-based mesoporous materials, nanoscale multicompartments and metamaterials are all applications that require such high degree of structural control.

[1] Kostiainen, M. A.; Hiekkataipale, P.; Laiho, A.; Lemieux, V.; Seitsonen, J.; Ruokolainen, J.; Ceci, P. (2013). Nat. Nanotech. 8, 52.

[2] Mikkilä, J., Anaya-Plaza, E., Liljeström, V., Caston, J. R., Torres, T.; De La Escosura, A. & Kostiainen, M. A. (2016). ACS Nano 10, 1565.

[3] Anaya-Plaza, E., Aljarilla, A., Beaune, G., Nonappa, Timonen, J. V. I., de la Escosura, A., Torres, T. & Kostiainen, M. A. (2019). Adv. Mat. 31, 1902582.

[4] Beyeh, N. K., Nonappa, Liljeström, V., Mikkilä, J., Korpi, A., Bochicchio, D., Pavan, G. M., Ikkala, O., Ras, R. H. A. & Kostiainen, M. A. (2018). ACS Nano 12, 8029.

[5] Liljeström, V., Mikkilä, J. & Kostiainen, M. A. (2014). Nature Commun. 5, 4445.

[6] Liljeström, V., Ora, A., Hassinen, J., Heilala, M., Hynninen, V., Joensuu, J., Nonappa, Rekola, H., Törmä, P., Ikkala, O., Ras, R. H. A. & Kostiainen, M. A. (2017). Nature Commun. 8, 671.

The functionality of a protein depends on its unique three-dimensional structure, which is a result of the folding process when the nascent polypeptide follows a funnel-like energy landscape to reach a global energy minimum. Computer-encoded algorithms are increasingly employed to stabilize native proteins for use in research and biotechnology applications [1]. Here, we reveal a unique example where the computational stabilization of a monomeric α/β-hydrolase fold enzyme (T_m = 73.5°C; ΔT_m > 23°C) affected the protein folding energy landscape. Introduction of eleven single-point stabilizing mutations based on force field calculations and evolutionary analysis yielded catalytically active domain-swapped intermediates trapped in local energy minima. Crystallographic structures revealed that these stabilizing mutations target cryptic hinge regions and newly introduced secondary interfaces, where they make extensive non-covalent interactions between the intertwined misfolded protomers [2]. The existence of domain-swapped dimers in a solution is further confirmed experimentally by data obtained from SAXS and crosslinking mass spectrometry. Unfolding experiments showed that the domain-swapped dimers can be irreversibly converted into native-like monomers, suggesting that the domain-swapping occurs exclusively in vivo [2]. Our findings uncovered hidden protein-folding consequences of computational protein design, which need to be taken into account when applying a rational stabilization to proteins of biological and pharmaceutical interest.

References

[1] Markova K., Chmelova K., Marques S. M., Carpentier P., Bednar D., Damborsky J., Marek M. (2020). Decoding the intricate network of molecular interactions of a hyperstable engineered biocatalyst. Chemical Science 11, 11162-11178.

[2] Markova K., Chmelova K., Marques S. M., Carpentier P., Bednar D., Damborsky J., Marek M. (2021). Computational protein stabilization can affect folding energy landscapes and lead to domain-swapped dimers. ChemRxiv. Preprint. https://doi.org/10.26434/chemrxiv.13634021.v1

L-asparaginases are used in the treatment of Acute Lymphoblastic Leukemia (ALL). However, the currently utilized bacterial-type enzymes cause several severe side effects. Therefore, there is an urgent need to develop a new generation of therapeutic L-asparaginases. Promising candidates can be found among plant-type L-asparaginases, which function as Ntn-hydrolases. Ntn‑hydrolases are produced as inactive precursors and develop enzymatic activity in an autoproteolytic maturation process. Unfortunetely, therapeutic use of wild-type (WT) plant-type enzymes is not possible due to their low substrate affinity (mM). Random mutagenesis is a protein engineering tool that can be used to enhance enzyme efficiency and study structure-function relationship. In this project, locally performed random mutagenesis was used to generate a library of mutants of plant-type L-asparaginase from E.coli (EcAIII). Several new variants of EcAIII were selected from the library and subjected to detailed structural (X-ray crystallography) and biophysical studies (nanoDSF, CD, activity/autoproteolytic tests).

The results of our studies revealed that autoproteolysis and enzymatic activity of EcAIII are unrelated events. Some variants of EcAIII retained the ability to autoprocess even in the absence of Arg207 (Fig. 1C), which is critical for catalysis and important for maintaining a H-bond network in the active site. Screening of thermal stability by nanoDSF showed that all analyzed unprocessed EcAIII variants had decreased T_m with respect to the WT enzyme. Thermal stability of variants cleaved into the mature aβ subunits varied, but some mutants with increased T_m were also found (Fig. 1A). Crystallization experiments proved that it was possible to obtain crystals of all variants cleaved into subunits. This was in stark contrast to the unprocessed mutants, which did not produce any crystals despite of extensive screening. This effect may be related to the presence of a highly disordered a-β linker in the uncleaved proteins. CD spectra showed that most of the unprocessed mutants are folded like the WT protein; however, some variants with significant changes in the CD signal were also found. The determined crystal structures (resolution 1.6-2.4 Å) showed that the active site of EcAIII is flexible enough to accept different amino acid substitutions; however, the type of substitution affects the H-bond pattern in the active site. Absence of Arg207 affects the overall conformation of the protein and leads to significant shifts of atomic positions in the entire enzyme molecule (Fig. 1B), as illustrated by the Cα rmsd value of 1.10 Å.

Work supported by National Science Centre (NCN, Poland) grants 2020/38/E/NZ1/00035 and 2019/03/X/NZ1/00584.

Pseudo symmetric, repeat proteins are favoured targets for computational protein design as they allow for the creation of larger domains with limited amino acids by exploiting their symmetric and repeating nature. One of the most common pseudo symmetric, repeat domains is the β-propellers fold. In addition, they fulfil many functions from sugar binding to enzymatic and protein-protein interaction mediation, thus increasing the potential applications of the designed proteins. Each propeller is built from 4-stranded anti-parallel β-sheets also known as a blade, repeated around a central axis. The number of blades differs from four to ten with seven and eight being the most common. The first successful computational protein design of a β-propeller was the 6-bladed Pizza protein¹. The RE3volutionary design method² makes use of ancestral sequence reconstruction and symmetry based template construction methods incorporated in Rosetta. Each blade of the pizza protein possess the same amino acid sequence. When two or three repeats of this sequence are expressed, they self-assemble into the 6-bladed domain.

The same design method was employed to design the eight or nine bladed Cake protein³. The protein consists repeating units of 42 amino acids, when eight repeats are expressed, the protein adopts the nine bladed fold. However, when nine repeats are expressed, the protein will adopt a nine bladed fold. This structural plasticity was unseen among β-propellers monomers. Its existence might explain the wide diversity of repeat numbers observed in β-propellers by allowing the change from even to odd numbers. Identical to the Pizza protein, smaller repeat fragments of Cake will self-assemble into either the eight-bladed protein or the nine-bladed protein. The structures of most these assemblies as well as the monomeric eight-and nine-bladed propellers were confirmed with X-ray diffraction experiments.

While the structural plasticity of the Cake protein is novel, we also wanted to create a protein that could only adopt the rare nine-bladed propeller fold. In order to achieve this a three-blade repeat (124 amino acids) was designed with a similar design strategy, with the idea the three-fold symmetry would prevent formation of eight bladed propellers. Two variants, Scone-E and Scone-R were created⁴. Crystallography revealed however that both designs adopted an eight-fold conformation. This failed design showcases that more research is needed to create a specific sequence for large β-propellers. In addition to this the Scone-E protein could only be crystallized upon addition of the polyoxometalate STA. This charged molecule interacts with multiple positively charged regions on the protein surface, neutralizing them. It can also bind multiple chains thus facilitating protein contacts, resulting in higher symmetric space groups.

Some of the designed proteins in this research behaved unexpectedly, thus illustrating the importance of accurate structure determination by X-ray diffraction to validate the designed proteins. In addition the design lessons on larger β-propellers could prove instrumental in the design of new functional proteins based on this common natural protein fold.

1. Computational design of a symmetrical β-propeller, Arnout R.D. Voet, Hiroki Noguchi, Christine Addy, David Simoncini, Daiki Terada, Satoru Unzai, Sam-Yong Park, Kam Y. J. Zhang, Jeremy R. H. Tame Proceedings of the National Academy of Sciences Oct 2014, 111 (42) 15102 15107; DOI: 10.1073/pnas.1412768111

2. Evolution-Inspired Computational Design of Symmetric Proteins, Arnout R. D. Voet, David Simoncini, Jeremy R. H. Tame, Kam Y. J. Zhang, Computational Protein Design, 2017, Volume 1529 ISBN : 978-1-4939-6635-6

3. Structural plasticity of a designer protein sheds light on β‐propeller protein evolution, Mylemans, B., Laier, I., Kamata, K., Akashi, S., Noguchi, H., Tame, J.R.H. and Voet, A.R.D. FEBS J, 2021, 288: 530-545. https://doi.org/10.1111/febs.15347

4. Crystal structures of Scone, pseudosymmetric folding of a symmetric designer protein, Bram Mylemans, Theo Killian, Laurens Vandebroek, Luc Van Meervelt, Jeremy R.H. Tame, Tatjana N. Parac-Vogt, Arnout R.D. Voet bioRxiv 2021.04.12.439409; doi:https://doi.org/10.1101/2021.04.12.439409

Fluorescent proteins (FPs) play an indispensable role in advanced imaging techniques. Such proteins are considered as “smart labels” allowing scientists to overcome the diffraction barrier of conventional light microscopy to visualize subcellular events. Since the first discovery of GFPs in the 1960s [1], numerous studies have been conducted to design new fluorophores not only covering the whole visible light from cyan to far-red region but also displaying improved photochemical performances. Furthermore, the FP technology gains remarkable achievements by developing successfully special classes of FPs which exhibit photo-transformable properties including photoactivation (PA), irreversible photo-conversion (PC) and reversible photo-switching (RS) [2]. Currently, irreversible photoconvertible and reversible photo-switchable FPs attract wide interest of scientists due to their potential of converting from an emissive state to another emissive state or switching between a fluorescent on and a non-fluorescent off state, respectively. The combination of reversibly switchable behavior and spectrally different emission has enabled application of multicolored super-resolution microscopy techniques in live-cell imaging. However, various drawbacks of currently used reversibly switchable red FPs (rsRFPs) have limited their application greatly and made them still being the least used in GFP-like proteins family. Moreover, the structure-function relationship and the mechanism controlling photo-switching behavior of rsRFPs have not been understood completely. Therefore, structural studies are essential to provide valuable information for the rational design of improved rsRFPs which fit better to experimental requirements.

The rsCherry protein was the first reported reversibly switchable red FP which was developed from mCherry – a good label in imaging techniques [3]. However, due to the non-optimal properties of rsCherry such as limited brightness, poor photostability and low contrast between on and off states [4]its application in super-resolution microscopy was not very widespread. Our current study has shown that rsCherry lost its absorption at 572 nm as well as fluorescence when it aged, despite being well protected from light, making studying its molecular structure and photo-mechanisms challenging. We were able to identify that the time-dependent bleaching in rsCherry is related to chromophore modifications and proposed that oxygen, a critical external reagent in the maturation process of FPs, is involved in unexpected chemical reactions of the chromophore. Spectroscopic data, native MS results and mutagenesis analysis, and especially structural studies of rsCherry crystallized in strictly anaerobic conditions strongly confirm our hypothesis that oxygen diminishes the rsCherry fluorescence through modifying its chromophore. These findings can help to develop improved red fluorescent proteins suitable for specific advanced imaging techniques.

Single-Molecule Magnets (SMMs) are coordination compounds that exhibit slow relaxation of magnetization of molecular origin. In the case when SMMs contain only one paramagnetic metal center we distinguish the group of so-called Single-Ion Magnets (SMMs) [1]. In SIMs, the occurrence of slow relaxation of magnetization is closely related to the existence of non-negligible magnetic anisotropy on the magnetic center of the molecule. Since the magnetic anisotropy is strongly influenced by the topology and strength of the applied ligand field it could be expected that significant prolongation of coordination bonds or occurrence of non-covalent interactions involving the metal center may have a fundamental impact on resulting magnetic properties.

In 2016, we reported on static and dynamic magnetic properties of compound [Co(dpt)(NCS)₂], (dpt = 1,7-diamino-4-azaheptane). Two non-covalent interactions between the Co(II) atoms and π electrons of NCS^- ligands from the neighboring complex molecule (d(C···NC_centroid) = 3.55 Å) caused a mediation of ferromagnetic exchange interaction within the centrosymmetric dimer and also the dynamic magnetic properties were affected markedly [2]. This inspired us to investigate in greater detail the magnetic properties of Co(II) compounds having some of their metal-ligand bonds at distances longer than typical coordination bonds.

Semicordination bond can be considered as a non-covalent analogue of the coordination bond, which occurs when a weak attractive non-covalent interaction between an electrophilic region (associated with a metal center) and a nucleophilic region (associated with a nonmetal atom in another or in the same molecular entity) is formed [3,4]. In typical semicoordination bonds, the distances between the metal atoms and electron-donating groups are significantly longer than the sum of their covalent radii but shorter than the sum of van der Waals radii, the interactions are dominantly of electrostatic character and topology of electron density between the particular atoms exhibits bond path and critical point [4].

In line with the above-mentioned considerations, we chose to investigate three different series of mononuclear Co(II) compounds: (a) [Co(2NH₂-R^₁-py)₂(R^₂COO)₂], where R^₁ = H, 3/4/5-CH₃, R^₂ = CH₃, C₆H₅, t-Bu, the carboxylate ligand form Co-O bonds with lengths of 2.0 – 3.1 Å, (b) [Co(bq)(NO₃)₂(ROH)], where bq is 2,2'-biquinoline and ROH are various alcohol ligands, one of the nitrate ligands forms the Co-O bond with lengths of 2.5 – 3.3 Å, (c) [Co(R-pymep)₂], where H-R-pymep are various derivatives of 2-{(E)-[(pyridin-2-yl)imino]methyl}phenol, two Co-N bonds with lengths between 2.5 and 2.7 Å. We studied these compounds by a combination of experimental (X-ray diffraction, magnetometry, HF-EPR) and theoretical (DFT, CASSCF, Electronic localization function, non-covalent interaction index, and QTAIM) methods. In this talk, we report on the character of semicoordination in these compounds and the relationship between the structure and observed magnetic properties.

[1] Craig, G.A., Murrie, M. (2015). Chem. Soc. Rev. 44, 2135-2147.

[2] Nemec, I. et al. (2016). Dalton Trans. 31, 12479–12482.

[3] Ananyev, I.V. et al. (2020). Acta Cryst. B. 76, 436-449

[4] Efimenko, Z. M. et al. (2020). Inorg. Chem. 59, 2316–2327.

C-H and Si-H bond activation by metal-hydrogen bonding (agostic interactions) plays a central role in catalytic processes [1]. These processes are directly dependent on metal-hydrogen bond energies. The versatility of the coordination modes of the heavy metals allows wide structure and topology variations of the complexes. Therefore, it is of major importance to accurately describe these chemical bonds.

One important drawback is the difficulty of deriving accurate and precise hydrogen atom positions by any kind of experiment. Neutron-diffraction experiments would be the only reliable source of such information, but there is a lack of available accurate X-H bond distances with X being a transition metal from neutron diffraction. Therefore, it would be desirable to determine both the elongation of the C-H and Si-H bonds in agostic interactions and the metal-hydrogen bonding parameters from standard X-ray diffraction experiments. In this context, the capabilities of Hirshfeld Atom Refinement [2] to obtain precise and accurate C-H/Si-H…X bond parameters (with X=transition metal) are tested.

Experimental and theoretical charge densities of agostic interactions involving transition metal compounds have been determined and analyzed in the past [3]. Here, we use a combination of HAR with subsequent X-ray constrained wavefunction fitting [4] and purely theoretical calculations on the accurate HAR and neutron geometries to analyze the related chemical bonding beyond a charge-density analysis. We use three different test systems: Figure 1a shows Si-H…Cu/Ag interactions enforced through the ligands used by proximity constraints. We discuss whether there are signatures of agostic interactions in these systems with closed-shell (d¹⁰) coinage metal atoms. [5] Figure 1b shows a system where the proximity enforcing ligands have caused an oxidative addition reaction so that the hydrogen atom is now more closely bonded to the transition metal in a Rh-H…Si interaction. We analyze again to which extent (inverse) agostic interactions are present in this system. [6] Our findings will be referenced against classical C-H…Ti agostic interactions found in titanium amides (Figure 1c).[7]

Figure 1. Compounds (a) 1·MCl (M = Cu, Ag). Metal hydrides (b) RhH, (c) Titanium amide compounds.

[1] Bäckvall, J. E. (2002). J. Organomet. Chem. 652(1-2), 105-111.

[2] Jayatilaka, D., Dittrich, B. (2008). Acta Cryst. A, 64, 383-393.

[3] (a) Scherer, W., Wolstenholme, D. J., Herz, V., Eickerling, G., Bruck, A., Benndorf, P., Roesky, P. W. (2010). Angew. Chem., Int. Ed., 49, 2242-2246. (b) Hauf, C.; Barquera-Lozada, J. E.; Meixner, P.; Eickerling, G.; Altmannshofer, S.; Stalke, D.; Zell, T.; Schmidt, D.; Radius, U.; Scherer, W. (2013). Z. Anorg. Allg. Chem., 639, 1996-2004.

[4] (a) Jayatilaka, D. (1998). Phys. Rev. Lett. 80, 798-801. (b) Jayatilaka, D., Grimwood, D. J. (2001). Acta Cryst. A, 57, 76-86.

[5] Hupf, E., Malaspina, L. A., Holsten, S., Kleemiss, F., Edwards, A. J., Price, J. R., Kozich, V., Heyne, K., Mebs, S., Grabowsky, S., Beckmann, J. (2019). Inorg. Chem., 58 (24), 16372-16378.

[6] Holsten, S., Malaspina, L.A., Mebs, S., Hupf, E., Grabowsky, S., Beckmann, J. (2021) Organometalics. Under revision.

[7] Adler, C., Bekurdts, A., Haase, D., Saak, W., Schmidtmann, M., & Beckhaus, R. (2014). Eur. J. Inorg. Chem., 8, 1289-1302.

Single-ion magnets (SIMs) are a class of metal-organic coordination complexes with the intriguing ability to sustain a magnetic moment after the removal of a magnetizing field [1]. This ability originates in orbital angular momentum of unpaired electrons, introducing magnetic anisotropy that increases the magnetic relaxation time of the SIM magnetic moment. Magnetic anisotropy is therefore a key property in the search for new and improved SIMs, and it is imperative to be able to measure magnetic anisotropy experimentally.

In 2002, it was shown that polarized neutron diffraction from single crystals (PND) could be used to obtain information on so called ionic site-susceptibilities [2], which are tensor quantities that show the response of the magnetic moment of the ion to an external magnetic field. Site susceptibilities give direct access to the magnetic anisotropy of a compound, and we have earlier used this technique to measure the magnetic anisotropy of both lanthanide and transition metal SIMs in single crystals [3, 4]. Importantly, the technique was recently extended for application to powder samples [5].

Utilizing this exciting development, we have performed polarized neutron powder diffraction (pPND) on the SIM CoCl₂(tmtu)₂, tmtu=tetramethylthiourea (1). The compound shows zero-field splitting and slow relaxation of its magnetic moment [6], both requirements for a SIM. With pPND we obtain the orientation of the magnetic anisotropy with respect to the molecular structure (Fig. 1), and follow its dependence on magnetic field strength, directly from a powder sample. Comparison with PND measured on a single crystal of the Br-analogue CoBr₂(tmtu)₂ (2) shows that the powder and single crystal techniques give comparable results.

In this contribution, I will discuss the site susceptibility model, the application of the model to both single crystal and powder data and the magneto-structural correlations that we obtain from these measurements. The extension of the technique to powders, and the dramatic reduction in data acquisition times that it entails, means that compounds can be studied, for which the growth of suitably sized crystals for single crystal neutron diffraction is unattainable. This opens the possibility for magnetic anisotropy studies on a much wider range of molecular magnetic compounds under a larger range of experimental conditions.

Metal-Organic Frameworks (MOFs) are a class of crystalline organic-inorganic hybrid materials derived from metal nodes and organic linkers, that exhibit features like high surface area, well-defined pore, tunable structures and their properties [1]. Use of redox-active metal nodes or organic linkers, stable radical based ligands can introduce a special feature like conductivity, electrocatalyst, electrochromic behavior in MOFs apart from their conventional uses such as gas storage, gas separation, etc. This idea is impeded mainly due to the insulating nature of organic linkers and the instability of the framework to the redox process. This hindered the study of electroactive MOFs until the last decade. Recent advancement in this field has directed a surge of interest in understanding their mechanism of charge transfer. MOFs are a unique platform to investigate the charge transfer mechanism where the corresponding metal ions or organic linkers are well defined in a highly crystalline rigid system. Charge transfer is directed by either the through-space or through-bond approach [2]. The through-bond mixed-valance charge transfer has been well explored whereas, through-space intervalency in MOF is rare [3].

We have synthesized a new Cobalt (II) based metal-organic framework using redox-active organic linker, N,N′-di(4-pyridyl)thiazolo-[5,4-d]thiazole (DPTTZ). The framework exhibits through-space intervalence charge transfer (IVCT) arise from cofacially arranged DPTTZ linkers (Figure 1). The IVCT is elucidated computationally using time-dependent density functional theory (TD-DFT) methods. The computational study also exploits the distance-dependent through-space intervalence charge transfer (IVCT) in this system.

Here, I will present experimental observation of through-space intervalence charge transfer (IVCT) using redox-active organic linkers in the metal-organic framework and its computational understanding using TD-DFT. This interrogation of charge transfer mechanism and electrical conductivity in MOF provides a better understanding of conducting materials.

[1] Furukawa, H., Cordova, K. E., O'Keeffe, M., Yaghi, O. M. Science 2013, 341, 1230444.

[2] Sun, L.; Campbell, M. G.; Dincă, M. Angew. Chem. Int. Ed. 2016, 55, 3566.

[3] Hua, C. et al. J. Am. Chem. Soc. 2018, 140, 6622.

[4] Nath, A. et al. (Manuscript under preparation)

Molecular framework materials can combine the functional properties typical of the traditional inorganic solid state, such as magnetism, with the remarkable tunability and flexibility that arises from the incorporation of molecular components. They therefore offer the opportunity to discover unusual behaviour that arises from the coupling of these properties.

We have recently shown that thiocyanate (NCS–) based frameworks are a fruitful ground for the study of these novel properties, as thiocyanate can both facilitate strong magnetic coupling (TCW>100K, [1]) and create intense optically absorption in the visible region [2]. Despite this, the rich chemistry of metal thiocyanates remains unexplored compared to the equivalent metal formates, azides or hypophosphites.

Our investigations of the functional properties of metal thiocyanate frameworks began with the simplest examples: the layered binary thiocyanates, M(NCS)2. We demonstrated, through powder neutron diffraction studies, that this M(NCS)2 family possesses a wide variety of interesting magnetic phases. As part of this investigation we synthesised three new binary materials, M = Cu, Mn, Fe; and demonstrated that their magnetic interactions are significantly stronger than the previously studied exemplars (M=Co,Ni) increasing |TCW| by a factor of four.[1] Our results also uncovered that Cu(NCS)2 is a good example of a quasi-1D quantum Heisenberg antiferromagnet which a significantly reduced ordered moment in its ordered state.[3]

We have also investigated the family of CsM(NCS)3 materials which adopt the 'post-perovskite' structure.[4] The post-perovskite structure type is so-called as it occurs at pressures beyond the stability field of conventional perovskites (e.g. MgSiO3, CaIrO3, NaMnF3), but these molecular post-perovskites readily form in standard solution chemistry. We find that this family of materials shows significantly reduced ordering temperatures and adopt non-collinear magnetic structures that give rise to considerable magnetic hysteresis.[5]

[1] E. Bassey et al., Inorg. Chem. (2020).
[2] M. Cliffe et al., Chem. Sci., 10, 793 (2019).
[3] M. Cliffe et al., Phys. Rev. B, 97, 144421 (2018).
[4] M. Fleck, Acta Crystallogr. C60, i63 (2004).
[5] M. Geers et al., in prep.

Single-molecule magnets (SMMs) are molecular compounds possessing a magnetic bistability of their ground state, allowing them to maintain the direction of induced magnetization for a significant amount of time, after having first applied an external magnetic field [1]. Understanding the driving force behind good single-molecule magnet properties and developing improved rational synthesis design of them go hand in hand. This has been demonstrated in recent years, with record-breaking magnetic properties found in SMMs that utilizes a single Dy(III) centre in a highly axial ligand field [2-3]. A compound designed with this in mind is the pentacoordinate [Dy(Mes*O)₂(THF)₂Br]3THF (Mes*: 2,4,6-tri-tert-buylphenyl, THF: Tetrahydrofuran, DyBrTHF), Figure 1 (left). In a recent study on this compound, the molecular environment was found to be critical for the magnetic properties [4].

One way of systematically changing the molecular environment is through induced hydrostatic pressure. The resulting structural changes can then be probed using X-ray diffraction (XRD), by utilizing a diamond-anvil cell (DAC). We have performed high-pressure single-crystal XRD at several pressure points up until 2.9(2) GPa, and analysed the ensuing structures. Looking at the first coordination sphere, we can investigate how the applied pressure alters the molecular environment of Dy, Figure 1 (middle). At the last two pressure points, a slight drop is noted for some of the Dy-O bonds.

The magnetic properties of SMMs are closely tied to their electronic structure, which can change when undergoing external pressure, as investigated earlier in our group [5]. This information can be accessed through theoretical ab initio calculations, done here using CASSCF+NEVPT2 in ORCA. The found NEVPT2 energies of the Kramers doublets at varying pressure reveal a significant change in the energy levels, Figure 1 (right), perhaps due to the pressure-induced alteration of the ligand field.

Nowadays, electrochemical energy storage plays a major societal role due to its widespread technological applications. Host nanostructured materials have a crystal structure with insertion sites, channels and/or interlayer spacings allowing the rapid insertion and extraction of lithium ions with generally little lattice strain. Therefore they are used as electrode materials for batteries. Dynamic processes occurring in batteries can be studied by operando modality. Operando experiments provide a realistic representation of the reaction behavior occurring at electrodes, which permits to checking the structural and electronic reversibility of a battery system, while at least one full cycle is performed. For all these reasons, ex situ studies, which reflect a given state of charge (SOC) of electrode materials are now complemented by operando measurements using complementary tools such as X-ray diffraction (XRD) and spectroscopic techniques such as X-ray absorption spectroscopy (XAS).

X-ray absorption spectroscopy is a synchrotron radiation based technique that is able to provide information on local structure and electronic properties in a chemically selective manner. Operando synchrotron radiation x-ray powder diffraction (SR-XRPD) experiments allow monitoring the extended structure of a material during the intercalation/release process of ions.

The potentiality of the joint XAS-XRD approach in the newly proposed Prussian Blue-like cathodes materials for rechargeable batteries is here underlined.

Prussian blue analogous (PBAs) or metal hexacyanoferrates are bimetallic cyanides with a three-dimensional cubic lattice of repeating -Fe-CN-M-NC- units (where M=transition metals). Because of their peculiar structure exhibiting large ionic channels, interstices in the lattice and redox-active sites they have been proposed as active materials for electrodes in batteries. In our group, a series of PBAs have been synthesized, such as copper hexacyanoferrate (CuHCF), manganese hexacyanoferrate (MnHCF), titanium hexacyanoferrate (TiHCF), multi-metal doped hexacyanoferrate, as well as copper nitroprusside etc. In particular, this talk will be summarize results obtained in the case of copper hexacyanoferrate and copper nitroprusside, as well as the manganese hexacyanoferrate [1-5]. Sodium-rich manganese hexacyanoferrate (MnHCF) is gaining consideration as battery materials for the versatility toward several chemistries beyond lithium, the ease of synthesis, as well as their affordable cost of production. MnHCF is constituted only by earth-abundant elements, and it displays high operational voltages and high specific capacities. Since PBAs act as sponge-like materials towards water molecules, also in case of short time exposure to contamination, and both the electrochemical behavior and the reaction dynamics are affected by interstitial/structural water and adsorbed water, the effect of hydration is critical in determining the electrochemical performance. The electrochemical activity of MnHCF without extensive dehydration was investigated by varying the interstitial ion content through a joint approach using operando x-ray absorption fine structure (XAFS) spectroscopy conducted at the XAFS beamline in ELETTRA and multivariate curve resolution with alternating least squares algorithm (MCR-ALS), with the intent to assess the structural and electronic modifications occurring during sodium release and lithium insertion as well as the overall dynamic evolution of the system. The study is also complemented to the and operando XRPD. It was found that only a minor volume change (about 2%) is recorded upon cycling the electrode material against lithium.

[1] A. Mullaliu, G. Aquilanti, P. Conti, J. R. Plaisier, M. Fehse, L. Stievano, M. Giorgetti. Copper Electroactivity in Prussian Blue-Based Cathode Disclosed by Operando XAS. J. Phys. Chem. C, 122 (2018) 15868-15877.

[2] A. Mullaliu, M. Gaboardi, J. Rikkert Plaisier, S. Passerini, M. Giorgetti. Lattice Compensation to Jahn-Teller Distortion in Na-rich Manganese Hexacyanoferrate for Li-ion Storage: An Operando Study. ACS Appl. Energy Mater., 3, (2020) 5728–5733.

[3] A. Mullaliu, J. Asenbauer, G. Aquilanti, S. Passerini, M. Giorgetti. Highlighting the Reversible Manganese Electroactivity in Na-Rich Manganese Hexacyanoferrate Material for Li- and Na-Ion Storage. Small Methods, (2020) 1900529.

[4] M. Li, A. Mullaliu, S. Passerini, M. Giorgetti. Titanium Activation in Prussian Blue Based Electrodes for Na-ion Batteries: A Synthesis and Electrochemical Study. Batteries, 7 (2021) 5.

[5] A. Mullaliu, M.T. Sougrati, N. Louvain, G. Aquilanti, M.L. Doublet, L.Stievano, M. Giorgetti. The electrochemical activity of the nitrosyl ligand in copper nitroprusside: a new possible redox mechanism for lithium battery electrode materials? Electrochimica Acta, 257 (2017) 364–371.

The following researchers are kindly acknowledged: Angelo Mullaliu, Giuliana Aquilanti, Jasper R. Plaisier, Min Li, Stefano Passerini.

The magnetic response of a system is the result of several contributions to the magnetic anisotropy which come from a plethora of effects. In the case of thin ferromagnetic films, the local-scale and long-range structural details, including film thickness, and interface interactions (intermixing, alloying, oxidation etc.) have a deep impact on the magnetism. Once known, these features can be used to tailor the magnetic response of the system, however, to fully control the system response, a deep knowledge is required.

To contrast the high reactivity of some ferromagnetic films, a passivating overlayer can be used: in these cases, further degrees of freedom add up in the definition of the magnetic response due to the upper interface phenomena. A deep understanding of such complex systems requires to assess and isolate the fine details linked to the interactions at the interfaces, and to those occurring within the film itself. Also, the oxidation prevention provided by the capping layer should be verified in view of application purposes.

Such a challenging task can be pursued only by combining complementary, state of the art techniques. This work presents the results of in-situ synchrotron radiation techniques and Magneto-Optic Kerr Effect (MOKE) measurements on Gr/Co/Ir systems, i.e. Co films intercalated between Graphene and Ir(111) [1]. The contributions to the in-plane and out-of-plane magnetic response of the system were evaluated based on Grazing Incidence X-Ray Diffraction (GI-XRD), X-ray Absorption Near Edge Spectroscopy (XANES), and Extended X-ray Absorption Fine Structure (EXAFS). The Gr/Co/Ir system is particularly interesting as the understanding of its magnetic behaviour requires to explore the thickness and thermal dependencies of local-scale and long-range anisotropies, to assess interface intermixing phenomena, and to evaluate the evolution of Co oxidation states (especially upon exposure to ambient conditions).

The development of effective catalytic processes for the conversion of CO₂ into value-added chemicals or fuels, such as methanol synthesis or the dry reforming of methane (DRM) relies strongly on a rational catalyst design, which in turn requires an in-depth understanding of structure-activity relationships. Due to the inherent complexity of heterogeneous catalytic systems, an arsenal of complementary techniques is required to characterize the catalytic structure (and dynamics thereof) from the atomic-to-nanoscale (under reaction conditions). In this talk, we show how the application of combined X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) allows obtaining the oxidation state, the local and (nano)crystalline structure of the catalysts providing the basis for the formulation of structure-performance relationships in catalysts for CO₂ valorization reactions.

In the first example, we demonstrate how a combined operando XAS-XRD experiment allowed us to relate the evolution of the structure of In₂O₃ nanoparticles (NPs) to their activity for CO₂ hydrogenation to methanol.^[1] The experiments revealed a reductive amorphization of the In₂O_3−x nanocrystallites with time on stream (TOS), leading ultimately to an over-reduction of In₂O_3−x to (molten) In⁰, in a process that is linked to catalyst deactivation. When the In₂O₃ NPs were supported on a nanocrystalline monoclinic ZrO₂ support, we observed the stabilization of the oxidation state of In via the formation of a solid solution m-ZrO₂:In.^[2] In the second example, we explore a Ni-Fe-based catalyst for the DRM. Combined, operando XAS-XRD experiments allowed us to probe the dynamics of Ni-Fe alloying/dealloying with the formation of FeO to explain the superior stability of the NiFe catalysts compared to a Ni-based analogue, due to a Fe-FeO_x-based redox cycle.^[3] In the last example, combined XAS–XRD experiments are used to shed light on the formation of Ru⁰ nanoparticles (ca.1 nm) via their exsolution from defective, fluorite-type Sm₂Ru_xCe_2−xO₇ solid solutions. The resulting exsolved nanoparticles show a high activity and stability for the DRM.^[4]

In this work, we present new geochemical and structural data in order to document a new occurrence of andradite garnet (garnet general formula {X}₃Y₂(Z)₃O₁₂) “demantoid” variety” in Sardinia, Italy [1]. The crystal structure consists of a framework of alternating ZO₄ tetrahedra and YO₆ octahedra that share corners, with cavities in the X cations coordinated by 8 oxygen atoms in the form of a triangular dodecahedron. The yellowish-green to intense green variety of andradite, called “demantoid”, is a precious and greatly appreciated gemstone, mainly found in Russia, Namibia, Madagascar and Italy (Valmalenco, Lumbardy) [2]. The studied samples come from a new deposit from Domus de Maria municipality, nearby “Sa Spinarbedda” mine. This found is very peculiar, because although the beauty of these samples, it has not been previously described from Sardinia region. In this work we investigated the structural and chemical features of these new demantoid samples by combining electron microprobe analyses (EMPA), laser ablation-inductively coupled mass spectrometry (LA-ICP-MS), single crystal X-ray diffraction (XRSD), IR and X-ray absorption (XAS) spectroscopies. Chemical analyses revealed an enrichment of Ca and Fe and a low content of Ti, Mn and Al, thus confirming the andradite nature of the garnet. The Cr content (~8.73 ppm, mean) has been useful to confirm the demantoid variety of andradite. Fe and Mn K-edge XAS data were collected at the XAFS beamline (ELETTRA, Trieste, Italy) both in transmission (Fe) and fluorescence mode (Mn), using fixed exit Si (111) monochromator [4] to better understand the coordination number of both ions. Position of the absorption edge together with the pre-edge peaks analysis, point to the presence of only Fe³⁺ in octahedral coordination, confirming that the whole Fe content can be allocated in the Y crystallographic site. A more complex situation has been found for Mn where pre-edge peaks analysis on our spectrum indicate that Mn should be mainly in the form of Mn²⁺ and 8-fold coordination, occupying the X crystallographic site, beside a small amount of Mn³⁺ is probably present in octahedral Y site. The infrared spectra of andradite crystals investigated at the SISSI beamline (ELETTRA, Trieste, Italy) show a prominent absorption band at about 3560 cm^-1, suggesting the well-known hydrogarnet substitution of (SiO₄)₄ with (O₄H₄)₄ [5][6]. These absorption features are related to hydroxide, which can be incorporated in the andradite structure in the form of structurally bonded OH groups, according to previous experimental findings [5]. X-ray single-crystal diffraction experiments refinement (Ia3̅d space group) highlighted a unit cell volume (1757.15(2)ų) larger than that reported usually in the literature thus confirming the presence of a slight water content [5]. The dodecahedral site X resulted to be partially occupied in a proportion of ≈96.2% Ca and ≈3% of Mn⁺². The octahedral site Y also resulted to be partially occupied in a proportion of ≈95.6% Fe⁺³ and ≈4.5% Al, while the Mn⁺³ content was too low to be estimated. Then, according to Adamo et al. (2011) [6] the potential partial occupation of tetrahedral site has been checked. Actually, the site resulted occupied only for ≈98%, the other 2% has been refined for O (same position and same thermal factor), suggesting the presence of structural water. Refining the site occupancy factor (s.o.f.) at the Si-site, modelled with the scattering curve of silicon alone in the X-ray structure refinement, we obtained s.o.f. value ≈98%, which barely confirmed potential hydrogarnet substitution [i.e., ((SiO₄)₄ with (O₄H₄)₄].

[1] Grew, Edward & Locock, A. & Mills, S.J. & Galuskina, Irina & Galuskin, Evgeny & Hålenius, Ulf. (2013). Am. Min. 98, 785-811.

[2] Štubňa, J., Bačík, P., Fridrichová, J., Hanus, R., Illášová, Ľ., Milovská, S., ... & Čerňanský, S. (2019). Minerals, 9(3), 164

[3] Geiger, C. A., & Rossman, G. R. (2020). Am. Min. 105(4), 455–467

[4] Di Cicco, A., Aquilanti, G., Minicucci, M., Principi, E., Novello, N., Cognigni, A., & Olivi, L. (2009). J. Phys. Conf. Ser. 190(1), 012043

[5] Amthauer, G. & Rossman, G.R. (1998): The hydrous component in andradite garnet. Am. Mineral., 83, 835–840.

[6] Adamo, I., Gatta, G. D., Rotiroti, N., Diella, V., & Pavese, A. (2011). Eur. J. Mineral. 23(1), 91-100

LiFePO₄ (LFP) as a cathode material in lithium ion batteries has a number of advantages including a long cycle life, a long calendar life and can be used at high discharge currents. A low cost, low energy hydrothermal synthetic route is being investigated where homemade Teflon bombs are used in an oven at 120^oC to synthesise LFP. During synthesis an aqueous LiOH solution is added dropwise to a FeSO₄–H₃PO₄ solution. All solutions are constantly purged with nitrogen during this step to prevent any oxidation. Interestingly it was determine that the rate at which the Li⁺ solution was added to the Fe²⁺ solution (while being stirred at a constant speed) influenced the final product. The addition rate was set to one drop every 1, 2, 3, 4 and 5 seconds. If the Li⁺ was added too slowly a mixture of phases (LFP and Li₃PO₄) was formed and when it was added too fast a completely different final phase was formed. In the latter case no LFP was identified using PXRD, but raman spectroscopy (RS) showed that non-crystalline LFP was present in the sample together with other phases.

A range of different techniques have been combined to probe the effect of the different addition rates on the local and average environments. It was determined that the 3sec addition rate was the optimum rate. Synchrotron X-ray diffraction (SXRD) with Rietveld refinement was used to characterize the average structures of the different environments (Figure 1). Mössbauer spectroscopy (MS) was used to probe the effect of Li⁺ addition on the local environment. Although no impure phases were identified using SXRD in the samples synthesised with the optimum addition rate, MS indicated that there was amorphous phases present. MS also showed that there was more than one Fe environment present in the sample. The major phase was Fe²⁺ in a distorted octahedral environment (LiFePO₄). The other 3 contributions to the total Fe in the sample are due to either structural defects, distortions or disorder [1]. X-ray absorption spectroscopy (XAS), in particular extended X-ray absorption fine structure (EXAFS) (Figure 2) was used to determine what the effect of the different addition rates on the local structure is.

Noble metal nanoparticles, due to their relatively high stability and wide scope of application, attract a lot of researchers’ attention. The catalyst effectiveness directly depends on the dispersion rate and the presence of active catalytic sites, since the higher the dispersion, the greater the surface area available for catalytic reactions. The substrate material also plays a large role in the efficiency of the final product. One of the new and effective methods for the synthesis of the noble metals ultrafine nanoparticles is UV irradiation of their precursor salts. The main advantages of this method are relative simplicity, high recovery rate and environmental friendliness. The nanoparticles synthesized in this way are less susceptible to agglomeration, which eliminates the need for introducing various surfactants and toxic solvents into the system, in contrast to standard methods. Due to the relatively high value of the electrode potential of the Pd²⁺/Pd⁰ pair, as well as low photostability, complex palladium salts are quite easily restored, and the selection of the optimal salt and radiation power allows the process to be rapidly carried out.

In this work, palladium nanoparticles were synthesized in an aqueous solution by UV irradiation using complex palladium oxalate as a precursor. The synthesis consists of UV irradiation of an aqueous dispersion of CeO₂ containing the [Pd(C₂O₄)₂]^2– complex as one of the most photoactive non-toxic precursors. Cerium dioxide was synthesized by a simple one-step method and was selected due to its high thermal stability and relative chemical inertness, as well as its large oxygen storage capacity due to the formation of the Ce⁴⁺/Ce³⁺ redox pair, which allows CeO₂ to efficiently release catalytically active oxygen species. Samples were studied by various laboratory methods, such as TEM, XRF, XRPD, XAFS spectroscopy, and diffuse reflection IR spectroscopy of CO probing molecules.

TEM images did not allow to distinguish Pd nanoparticles from the substrate material but showed the absence of the UV radiation influence on the sizes of CeO₂ nanoparticles. XRF data showed the presence of cerium and palladium atoms in the material. X-ray diffraction patterns indicate the presence of both a cerium dioxide phase and a phase of metallic palladium, while the analysis of XAFS spectra beyond the K edge of palladium also showed the presence of a PdO phase in the system (Fig. 1). The approximate size of palladium nanoparticles was estimated from the infrared spectra after CO adsorption (Fig. 2) and it was less than 2 nm, which is significantly smaller than the average size of Pd nanoparticles obtained by a similar method without a CeO₂ substrate (1.5–9.5 nm) [1].

[1] Navaladian, S., Viswanathan, B., Varadarajan, T. K., & Viswanath, R. P. (2008). Nanoscale research letters 4(2), 181.

The work was supported by grant of President of Russia for young scientists (MK-2730.2019.2).

The use of UV-visible light responsive catalysts in hydrogen production is of high interest owing to reduced energy and environment resources. Here, we present a highly efficient system for photocatalytic hydrogen production, comprising ordered silicate nanochannels embedded with novel visible-light-responsive catalytic phosphotungstic acids (PTA) along the silicate channel walls and arrayed co-catalytic platinum nanoparticles within the channels. The UV-visible-light-responsive PTA catalyst is synthesized by replacing a corner WO⁴⁺ of PTA with Ni for Ni-ℓPTA, and then embedded onto the walls of hexagonally packed silicate channels during synthesis at an air-liquid interface. In situ grazing incidence small-angle X-ray scattering on the air-liquid interface [1-2] evidences multi-step formation processes of the ordered and oriented silicatropic template PMS and the subsequent formation of Pt NP arrays in the PMS template. Suggested by the X-ray results, the latter process involves anion exchange of the Pt-metal precursors and the surfactant micelles of the silicate PMS channels, upon UV-visible light irradiation. The hence formed composite Pt-NP@Ni-ℓPMS, with closely packed catalytic pairs of Pt-NP and PTA, demonstrates a high hydrogen production rate upon light illumination, due presumably to efficient generation and transport of photo-electrons. The efficiency of H₂-production surpasses greatly that of PMS or Ni-ℓPMS with or without randomly disperse Pt nanoparticles.

Controlling the mesoscopic nature of materials through local interactions can lead to the formation of highly non-topologically trivial structures. The local interactions that lead to the emergence of mesoscopic structures, known as textures, is well understood in magnetic materials. The most studied textures are skyrmions as the have interesting applications in spintronics due to their topological nature and dynamic properties [1]. These features are thought to be exclusively a magnetic characteristic; however, they are purely topological in nature and arise due to a specific set of interactions which may not be limited to magnetic materials. As we have an increased understanding of what causes topological properties, we can design/search for specific interactions in non-magnetic materials that may lead to non-magnetic analogues of topologically protected phases.

For skyrmions to exist, three interactions must be present: symmetric exchange, antisymmetric exchange, and a coupling to a magnetic field [2]. To explore the possibility of creating analogues of magnetic textures in non-magnetic materials we replace magnetic dipoles with non-magnetic quadrupoles and exchange the magnetic field for a strain field and adapt the interactions accordingly. Here we look at the capability of MOFs to harbor analogous complex magnetic phases such as skyrmions. MOFs are the perfect candidates as there are a plethora of components to play with such as underlying lattice, guest species, and interactions between the framework and the guest.

Through density functional theory calculations, molecular dynamics simulations, and Monte Carlo simulations, we explore the extent to which these interactions may exist in chiral MOF frameworks with quadrupolar guests such as a benzene or CO₂ and how varying the relative strengths of the three interaction parameters with temperature effects the behaviour of the non-magnetic textures. Using small angle scattering we have been able to define six distinct phases, giving evidence of quadrupolar skyrmions and interesting textures which are not present in the dipolar analogue. This opens up the field to new ways of creating non-topologically trivial textures that could potentially be less restrictive than chiral magnets.

[1] S. Mühlbauer, B. Binz, F. Jonietz, C. Pfleiderer, A. Rosch, A. Neubauer, R. Georgii, and P. Boni, Science 323, 915 (2009).

[2] S. D. Yi, S. Onoda, N. Nagaosa, and J. H. Han, Phys. Rev. B. 80, 054416 (2009).

Artificial molecular machines promise applications in many fields, including physics, information technologies, chemistry as well as medicine. The deposition of functional molecules in 2D or 3D assemblies in order to control their collective behavior and the structural characterization of these assemblies are challenging tasks. We exploit porous materials to form rigid matrix for mechanochemical preparation of bulk or surface host−guest inclusions with functional molecules, such as molecular rotors, molecular motors and molecular switches.

Unambiguous determination of the molecular structure and monitoring of the molecular function such as rotation of a molecular rotor or on/off switching of a molecular switch cannot be studied by X-ray analysis because the systems are typically heavily disordered fine powders. We use solid-state nuclear magnetic resonance (SS-NMR) spectroscopy to obtain atomic-level insights into the structure and dynamics of these functional materials. SS-NMR spectra provide valuable information about structure, interactions and dynamics in solids not available otherwise.

It will be demonstrated that SS-NMR experiments provide unequivocal evidence of the formation of the 2D and 3D assemblies and can also be used for the observation of such a molecular function as the photoisomerization of a molecular switch deposited on a surface. We have also developed a solid-state NMR method for investigation of two dimensional arrays of light-driven molecular motors [1-4].

Figure 1. Examples of studied molecules. The shaft ensures deposition of the molecules in the porous molecular matrix, the stopper ensures surface deposition. The molecular motor is a unidirectional light-driven motor and the switch performs its function upon UV irradiation.

[1] Kaleta, J., Chen, J., Bastien, G., Dračínský, M., Mašát, M., Rogers, C. T., Feringa, B. L., Michl, J. (2017). J. Am. Chem. Soc. 139, 10486.

[2] Kaleta, J., Bastien, G., Wen, J., Dračínský, M., Tortorici, E., Císařová, I., Beale, P. D., Rogers, C. T., Michl, J. (2019). J. Org. Chem. 84, 8449.

[3] Santos-Hurtado, C., Bastien, G., Mašát, M., Štoček, J. R., Dračínský, M., Rončević, I., Císařová, I., Rogers, C., Kaleta, J. (2020). J. Am. Chem. Soc. 142, 9337.

[4] Dračínský, M., Santos-Hurtado, C., Masson, E., Kaleta, J. (2021). Chem. Commun. 57, 2132.

CO₂ is widely recognised as the main cause of greenhouse effect, causing global warming and climate change. With the aim to reduce CO₂ emissions, during the last decades, several strategies have been developed for the capture, utilization and storage of carbon dioxide (CCUS). This work focuses on the development of bifunctional catalysts for the conversion of CO₂ into dimethyl ether (DME), a fuel with no collateral emissions other than CO₂ and H₂O, a high cetane number and chemical-physical properties similar to LPG. DME is obtained from the reaction of CO₂ with H₂ through two subsequent reactions. The first one is the CO₂ reduction with H₂ to obtain methanol; this reaction is promoted by Cu-based catalysts like Cu/ZnO/Al₂O₃ and Cu/ZnO/ZrO₂. The second one is the dehydration of methanol to DME, catalysed by solid acidic catalysts, such as zeolites and γ-Al₂O_3.

In this work three different types of mesostructured acidic catalysts were synthesized: Al-SiO₂ (Al-SBA-15, Al-MCM-41), Zr-TiO₂ and γ-Al₂O₃. These materials were tested for methanol dehydration and used as supports for the Cu-based redox phase, to obtain composite materials to be used as bifunctional catalysts. Mesostructured matrix should limit the growth of redox phase nanoparticles inside the mesopores and assure a high dispersion due to the high surface area, leading to a high contact area between the two phases and, thus, granting in principle superior catalytic performances.

All mesostructured systems were synthesized via the Sol-Gel method, either through an Evaporation-Induced Self-Assembly (EISA) or a solvothermal approach, and characterized by XRD, TEM and N₂ physisorption. Acidic sites characterization was performed by calorimetry and FTIR spectroscopy using pyridine as a probe molecule. The catalysts were eventually physically mixed with a Cu/ZnO/Al₂O₃-based commercial redox catalyst and tested in a bench-scale plant with a fixed bed reactor for CO₂ conversion to DME. Mesostructured supports were used to disperse the CuO/ZnO/ZrO₂-based redox phase by a wet impregnation method combined with a self-combustion process or by a two-solvents impregnation strategy. The obtained bifunctional catalysts were characterized by PXRD, N₂ physisorption, TEM and HRTEM in order to determine the most promising synthetic conditions in terms of dispersion and nanosize of the active phase and textural properties of the corresponding composites.

Two methods are traditionally used to characterize gas adsorption properties in porous solids: volumetric and gravimetric. They have a number of limitations, but most importantly, they yield a macroscopic picture of interactions (properties), without access to a microscopic picture (mechanisms on an atomic level). Diffraction is commonly used as a complementary technique to explain these properties, giving insight into structure and thus revealing the underlying guest-host and guest-guest interactions. Various anomalies (deviations from a typical behaviour) detected by the macroscopic methods require an in situ diffraction experiment, aiming to identify the responsible phenomena like a guest rearrangement / repacking, framework deformation etc. Thus, a separate diffraction experiment is usually providing a microscopic picture for the properties found by other physico-chemical methods.

In this presentation we will show examples of using in situ powder diffraction to simultaneously access the structure and adsorption properties of a small pore crystalline solid. (Quasi)-equilibrium isotherms and isobars can be built directly from sequential Rietveld refinements, both on adsorption and desorption, thus addressing the hysteresis and kinetics of gas adsorption/desorption. Detailed picture of guest reorganization with an increasing uptake can be obtained. Note that the reorganization of the individual guest sites is not accessible to volumetric and gravimetric methods, as they give only total amounts of gas uptake.

Interestingly, the adsorption isobars and isotherms obtained directly from diffraction data can be fitted by known equations, such as a logistic function (isobars) or a Langmuir equation (isotherms). Thermodynamic properties, such as enthalpy and entropy of gas adsorption can be extracted from these curves. The limitations of this technique are very different from traditional methods, thus making it highly complementary.

Lastly, the adsorption kinetics can be followed by in situ powder diffraction at given P,T conditions versus time. The guest uptake extracted by a sequential Rietveld refinement can be fitted and analysed in terms of Arrhenius theory giving access to the activation energies for gas diffusion. Thanks to the microscopic picture these barriers can be tentatively attributed to various diffusion paths inside the solid.

This talk will be illustrated by examples of noble gas adsorption in a porous hydride, γ-Mg(BH₄)₂ [1], featuring 1D channels suitable to distinguish and likely separate some of these gases. Besides published results [2,3], a lot of unpublished data will be shown.

[1] Filinchuk, Y., Richter, B., Jensen, T. R., Dmitriev, V., Chernyshov, D. & Hagemann, H. (2011). Angew. Chem. Int. Ed. 50, 11162. [2] Dovgaliuk, I., Dyadkin, V., Vander Donckt, M., Filinchuk, Y. & Chernyshov, D. (2020). ACS Appl. Mater. Interfaces 12, 7710. [3] Dovgaliuk, I., Senkovska, I., Li, X., Dyadkin, V., Filinchuk, Y. & Chernyshov, D. (2021). Angew. Chem. Int. Ed. 60, 5250.

Complex early transition metal oxides have emerged as leading candidates for fast charging lithium-ion battery anode materials [1,2]. Framework crystal structures with frustrated topologies are good electrode candidates because they may intercalate large quantities of guest ions with minimal structural response. Starting from the empty perovskite (ReO₃) framework, shear planes and filled pentagonal columns are examples of motifs that decrease the structural degrees of freedom. As a consequence, many early transition metal oxide shear and bronze structures do not readily undergo the tilts and distortions that lead to phase transitions and/or the clamping of lithium diffusion pathways that occur in a purely corner-shared polyhedral network[1].

In this work, we explore the relationship between composition, crystal structure, and reduction pathway in a variety of recently synthesized mixed alkali, transition metal, and main group oxides (Fig. 1), moving beyond the archetypal Ti-Nb-O and W-Nb-O phase spaces. Solid-state NMR spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), synchrotron and neutron diffraction, and DFT are combined with electrochemical experiments to present a comprehensive picture of the charge storage mechanisms. Prospects for tunability and implications for charge rate and structural stability will be discussed.

[1] Griffith, K. J., Wiaderek, K., Cibin, G., Marbella, L. M. Grey, C. P. (2018). Nature 559, 556.

[2] Griffith, K. J., Harada, Y., Egusa, S., Ribas, R. M., Monteiro, R. S., Von Dreele, R. B., Cheetham, A. K., Cava, R. J., Grey, C. P., Goodenough, J. B. (2021). Chem. Mater. 33, 4.

This Interest in metal hydrides was initially driven by the potential to develop efficient and safe on-board hydrogen stores working close to ambient pressure and temperature. In search for hydrides with higher gravimetric storage capacity, the researchers concentrated on hydrides based on light atoms, among others on Li and Na salts containing hydroborate anions such as borohydride BH₄⁻ or closo-hydroborate B₁₂H₁₂²⁻ [1]. The hydrogen absorption-desorption cycling in complex hydrides still needs more chemical ideas due to relatively strong covalent bonding. Unexpectedly, the high mobility of alkali metal cations in some complex hydrides has opened the door for their application as battery materials, mainly as solid-state electrolytes (SSE).

Replacing the liquid electrolyte by SSE offers several advantages: i) a solid material is more thermally stable, thus enhancing the overall safety of the battery; ii) being less prone to the dendrite penetration, it enables the use of alkali metals as negative electrodes and iii) acting as physical layer between the two electrodes, it has a beneficial effect on the cell performance [2].

Among the different classes of SSE, the metal hydroborates have received particular interest, being soft, highly stable toward oxidation and exhibiting fast ion conductivity, enabled by an entropically-driven phase transition. Such transitions generally occur above room temperature (rt), and it is therefore necessary to frustrate the anionic lattice, for example by anion mixing to bring the superionic regime down to rt [3-6].

The hydrogen storage and mobility of the cations in light complex hydrides depends on the structural features, pathways available in the anion packing and on the anion thermal motion. While the latter requires important experimental and theoretical effort, the first two parameters can be easily quantified from crystal structures obtained by X-ray powder diffraction.

Examples of crystallography and crystal chemistry analyses of novel solid-state electrolytes as well as proof-of-concept Na-ion all-solid-state batteries will be shown.

[1] Paskevicius M. et al. Chem. Soc. Rev. 2017, 46, 1565

[2] Zeier W. & Janek J. Nat. Energy 2016, 1, 16141

[3] Tang W.-S. et al. ACS Energy Lett. 2016, 1, 659

[4] Duchêne L. et al. Energy Environ. Sci. 2017, 10, 2609

[5] Murgia F. et al. Electrochem. Comm. 2019, 106, 106534

[6] Brighi M. et al. Cell Reports Phys. Sci. 2020, 1, 100217

Diffraction experiments typically provide clear picture of a crystal structure and basis for understanding material properties. However, for materials with high static or dynamic disorder and/or weakly occupied atomic sites, e.g. ionic conductors, the diffraction data reflecting space- and time-averaged state may struggle to distinguish several alternative models yielding similar χ². In that case, atomistic modelling may help not only to identify the more energetically stable configuration but also provide insights into the mechanism of its formation. I will present several recent examples of studies of disordered oxide-ion and proton conductors, where ab initio static and geometry optimisation calculations and molecular dynamics simulations not only helped to validate neutron diffraction analysis but also revealed the mechanism driving the disorder.

Prussian blue analogues (PBAs) with formula A_xM[M’(CN)₆]_1-y.zH₂O, show considerable promise as highly sustainable electrodes in sodium ion batteries. PBAs are formed of metal that are octahedrally coordinated by cyanide groups which act as bridges between the metal centers. This corner linked framework creates a highly porous structure into which either cations such as Na⁺ or molecules such as H₂O can insert into. However, PBAs receive criticism on their thermal stability and moisture sensitivity, which can be detrimental to the electrochemical performance or compromise safety. However, existing pessimism towards the material is based on studies of traditional Prussian blue (Fe₄[Fe(CN)₆]₃), whereas the vacancy-free compounds such as iron hexacyanoferrate (Fe-HCF), Na_xFe[Fe(CN)₆]_1-y.zH₂O (x≈2, y≈0, z≈0), do not show any similarity in terms of structural transitions or performance in a battery. In this contribution, our efforts at understanding the thermal and moisture stability of vacancy-free Fe‑HCF are presented.

We have optimised a method of consistently producing Fe-HCF with <5% vacancies on the Fe(CN)₆ site. Consequently, the effect of sodium content and moisture on structure and stability has been independently quantified. In the absence of vacancies, the moisture sensitivity of the material is determined by the Na⁺ content, with a sodium-rich structure absorbing more water and binding with higher affinity. Interestingly, despite a higher moisture sensitivity, the Na⁺ rich system features higher thermal stability. The interplay between the host framework, sodium and water also appears to influence the phase transitions of the material. The sodium-free material does not undergo any phase transitions, remaining cubic (Fm-3m) from 4K to 300K, whereas the sodium rich (x>1.5) systems exhibit several phase transitions between R-3 and P2₁/n as a function of temperature and water content. These are driven by octahedral tilting (cf. perovskites) and given that such transitions are generally rare in PBAs, their presence within a single system provides a platform for investigating driving factors.

As described, the moisture sensitivity of PBAs is often understood as the tendency to absorb water into the bulk structure. However, water can negatively affect cation rich Fe-HCF via other mechanisms. We identified that contact with airborne moisture during storage can lead to a loss of capacity in Fe-HCF. The capacity fading mechanism proceeds via two steps, first by sodium from the bulk material reacting with moisture at the surface to form sodium hydroxide and partial oxidation of Fe²⁺ to Fe³⁺. The sodium hydroxide creates a basic environment at the surface of the PW particles, leading to decomposition to Na₄[Fe(CN)₆] and iron oxides. Although the first process leads to loss of capacity, which can be reversed, the second stage of degradation is irreversible. The combination of each process ultimately leads to a surface passivating layer which prevents further degradation.

Thus, the interaction of water with cation rich PBAs is complex and should not be overlooked. Gaining an understanding of the degradation mechanisms, including structural and chemical driving forces provides substantial insight into effective design strategies for increasing the performance.

The overarching goal of this work is to understand and overcome the performance limitations of industrially relevant battery materials using powder diffraction studies, both through ex situ studies of materials and operando studies of cycling battery cells. However, the normal modalities for the collection and analysis of powder diffraction data typically lack the sensitivity to resolve the structure of battery materials with sufficiently low uncertainty to effectively resolve structure-properties correlations. We have therefore been actively been developing new approaches to data collection and analysis that overcome these limitations, permitting us to obtain robust structure-properties correlations for industrially relevant cathode materials and for industrially relevant battery cell designs.

We have recently developed a novel perspective for systematically exploring occupancy defects which we have applied to the study of the important family of NMC battery cathode materials [1]. Using these f* diagrams, we have demonstrated sufficient sensitivity to site occupancies to resolve problems with the conventional atomic form factors used for X-ray diffraction – an error of about 3% in the case of oxygen. After correcting for these problems and robustly determining atomic displacement parameters, we have demonstrated the ability to unambiguously resolve the nature of key defects as well as to determine defect concentrations with an unprecedented sensitivity of ~0.1% (absolute), as judged by the agreement between independent refinements of synchrotron and neutron powder diffraction data. From the refined occupancies for a series of NMC compounds, it was possible to determine the energy associated with the formation of anti-site defects, and to conclusively demonstrate that the conventionally accepted mechanism for defect formation was incorrect [2]. Additionally, we have utilized rapid synchrotron powder diffraction methods to carry out multidimensional diffraction studies with fine resolution not just in time but in space as well. In this manner, it has been possible to resolve both vertical [3] and lateral [4] inhomogeneity in battery cells with a sensitivity to the local state of charge (SOC) of ~0.1%. The former has illuminated the performance limitations of exceptionally thick battery cathodes with very high energy densities, while the latter has allowed us to distinguish between different potential failure mechanisms.

[1] L. Yin, G. Mattei, Z. Li, J. Zheng, W. Zhao, F. Omenya, C. Fang, W. Li, J. Li, Q. Xie, J.-G. Zhang, M.S. Whittingham, Y.S. Meng, A. Manthiram and P. Khalifah (2018). Rev. Sci. Instrum. 89, 093002.

[2] L. Yin, Z. Li, G. Mattei, J. Zheng, W. Zhao, F. Omenya, C. Fang, W. Li, J. Li, Q. Xie, E. Erickson, J.-G. Zhang, M.S. Whittingham, Y.S. Meng, A. Manthiram, and P. Khalifah (2019). Chem. Mater., 32, 1002-1010.

[3] Z. Li, L. Yin, G. Mattei, M. Cosby, B.-S. Lee, Z. Wu, S.-M. Bak, K. Chapman, X.-Q. Yang, P. Liu, and P. Khalifah (2020). Chem. Mater., 32, 6358.

[4] G. Mattei, Z. Li, A. Corrao, C. Niu, Y. Zhang, B.-Y. Liaw, C. Dickerson, J. Xiao, E. Dufek, and P. Khalifah (2021). Chem. Mater., 33, 2378.

Most nanocrystals are expected to show deviations from a perfect crystal lattice inside the grains, which is referred to as modulation waves[1], because of their significant surface effects, leading to exceptional physical and chemical properties. Conventional X-ray diffraction fails to reveal modulation waves owing to the assumption of the periodic structure, whereas electron diffraction from a single grain is one of the most powerful probes to distinguish the core structure from the surface structure on the atomic level. It is, however, still challenging to investigate modulation waves from the core to the surface, which is the atomic-level core-shell structure. In this study, we have demonstrated that synchrotron X-ray total scattering makes it possible to visualize the core-shell structure on the picometer level in Pd nanocrystals.

X-ray total scattering provides a potential for visualization of modulation waves[2]; nevertheless its applications have been very limited because the approach is extremely demanding of experimental data. We have developed the high-resolution and high-accuracy total scattering measurement system, OHGI (Overlapped High-Grade Intelligencer), at SPring-8[3,4] to overcome the limitations. Recent studies have demonstrated that our total scattering data are of the highest quality in terms of both Bragg and diffuse scattering[5-7]. With this system, Pd nanocrystals were measured under hydrogen pressure. The total scattering data were converted into atomic pair distribution functions (PDF) on the basis of the principle of maximum entropy[8]. The resulting PDFs were virtually free from spurious ripples at no expense of real-space resolution. We have attempted to model modulation waves from the PDFs on the basis of an fcc Pd lattice. The model suggests that the interatomic distances between Pd atoms in the shell region are longer than those in the core by a few picometers. In addition, we found that the core-shell structure undergoes significant changes by hydrogenation. The picometer-level core-shell structure can explain that implied by neutron diffraction, where both tetrahedral and octahedral sites are occupied by hydrogen atoms in the surface[9]. In this presentation, I will discuss the relationship between the modified core-shell structure and hydrogen-storage kinetics in Pd nanocrystals.

[1] Hudry, D., Howard, I. A., Popescu, R., Gerthsen, D. & Richards, B. S. (2019). Adv. Mater. 31, 1900623.

[2] Palosz, B., Grzanka, E., Gierlotka, S. & Stelmakh, S. (2010). Z. Kristallogr. 225, 588.

[3] Kato, K., Tanaka, Y., Yamauchi, M., Ohara, K. & Hatsui, T. (2019). J. Synchrotron Rad. 26, 762.

[4] Kato, K. & Shigeta, K. (2020). J. Synchrotron Rad. 27, 1172.

[5] Svane, B., Tolborg, K., Kato, K. & Iversen, B. B. (2021). Acta Cryst. A77, 85.

[6] Pinkerton, A. (2021). Acta Cryst. A77, 83.

[7] Beyer, J., Kato, K. & Iversen, B. B. (2021). IUCrJ 8, 387.

[8] Kato, K. et al., submitted.

[9] Akiba, H., Kofu, M., Kobayashi, H., Kitagawa, H., Ikeda, K., Otomo, T. & Yamamuro, O. (2016). J. Am. Chem. Soc. 138, 10238.

Permanent magnets are key enablers driving the 21^st century’s diverse electromagnetic technologies [1]. Ceramic magnets based on iron oxides are corrosion resistant and cost-effective permanent magnetic materials with minimal ecological footprint, compared to their lanthanide-based counterparts (such as SmCo₅; Nd₂Fe₁₄B etc.) [1,2]. Among the ceramic magnets, the hexaferrites (AFe₁₂O₁₉; A = Ba/Sr) constitute the bulk of industrially produced permanent magnets [3,4]. A permanent magnet’s properties emerge hierarchically and are influenced by the structure on various length scales. From atomic interactions in the unit cell (~ 1–10 Å), through the interactions between crystallites/domains (~10 nm–1 µm), to the consolidated macroscopic forms (~ 0.1 mm–0.1 m), magnetism evolves over length scales spanning 10 orders of magnitude [5]! For maximal magnetic performance, the structure of a permanent magnet must be optimized at all levels. Control over the structure is obtained by controlling the synthesis and processing parameters. Additionally, these fabrication methods need to be economical, effective and compatible with industrial scale synthesis processes.

Recent work from our group has demonstrated the fabrication of high-performance nanostructured SrFe₁₂O₁₉ hexaferrite permanent magnets from solid-state processing of ferrihydrite – a poorly crystalline, structurally disordered nanomaterial [6,7]. This fabrication method is low-cost, scalable and compatible with industry processes. In the presence of Sr²⁺ ions, ferrihydrite is seen to act as a building block for the SrFe₁₂O₁₉ hexaferrite, irrespective of synthesis technique (hydrothermal/microwave/solid-state synthesis) [7–9]. While the transformation of ferrihydrite to hexaferrite has been documented in previous studies, a detailed understanding of the conversion process in situ is lacking. The fundamental question that remains to be answered: how does long-range crystalline order in the hexaferrite magnet arise from the nanoscale-disordered ferrihydrite precursor?

Here, we report on our efforts towards addressing this question using in­ situ­ synchrotron X-ray scattering studies to investigate the ferrihydrite-hexaferrite transformation. Ferrihydrite samples (with Sr²⁺) were heated while scattering data was collected in situ at the P02.1 beamline at PETRA III. The P02.1 beamline allows for 2 operating modes separately optimized for X-ray Bragg scattering and total scattering[10]. In situ X-ray scattering experiments were performed in both modes. Combining Rietveld modelling of Bragg scattering data and Pair Distribution Function (PDF) modelling of total scattering data provided detailed insight into the real-time structural evolution of disordered ferrihydrite to crystalline hexaferrite. PDF analysis shed light on the evolution of the short- and intermediate-range structural features during the transformation. Rietveld analysis helped ascertain the long-range order, nanoscale morphology and crystallite growth mechanism. This clear picture of the ferrihydrite-hexaferrite transformation over multiple relevant length scales is expected to aid future efforts in engineering better permanent magnets. Meanwhile, beyond permanent magnetic materials, these insights are also expected to contribute toward a broader understanding of the evolution of crystalline order from nanoscale disorder.

[1] Gutfleisch, O., Willard, M. A., Brück, E., Chen, C. H., Sankar, S. G., & Liu, J. P. (2011) Adv. Mater. 23, 821.

[2] Sugimoto, M. (2010) J. Am. Ceram. Soc. 82, 269.

[3] Pullar, R. C. (2012) Prog. Mater. Sci. 57, 1191.

[4] de Julian Fernandez, C., Sangregorio, C., de la Figuera, J., Belec, B., Makovec, D., & Quesada, A. (2020) J. Phys. D. Appl. Phys. 54, 153001.

[5] Skomski, R. (2003) J. Phys. Condens. Matter. 15, R841.

[6] Christensen, M. & Vijayan, H. Enhanced magnetic properties through alignment of non-magnetic constituents (2020) European Provisional Patent P5698EP00-CLI 2020.

[7] Vijayan, H., Knudsen, C. G., Mørch, M. I., & Christensen, M. (2021) Mater. Chem. Front. 5, 3699.

[8] Granados-Miralles, C., Saura-Múzquiz, M., Bøjesen, E. D., Jensen, K. M. Ø., Andersen, H. L., & Christensen, M. (2016) J. Mater. Chem. C. 4, 10903.

[9] Grindi, B., BenAli, A., Magen, C., & Viau, G. (2018) J. Solid State Chem. 264, 124.

[10] Dippel, A.-C., Liermann, H.-P., Delitz, J. T., Walter, P., Schulte-Schrepping, H., Seeck, O. H., et al. (2015) J. Synchrotron Radiat. 22, 675.

While simple associations exist between piezoelectric properties and processing history, there is considerable scope for design of materials based on a more detailed molecular understanding of the re-arrangements which underpin the piezoelectric phenomenon in silk fibroin.[1] Crystallinity, and the two-phase model of semi-crystalline model of polymers, are often used to understand the properties of protein based materials where there is considerable thermodynamic drive to short range ordering of polymer chains, folding, which is not present in melt processed thermoplastics. Our investigations aim to probe the relationship between structure and dynamics in silk fibroin based materials and correlate these with the piezo-electric signal.

Recently, we have used a triggered and summative data acquisition scheme to synchronise of X-ray scattering data with a piezoelectric cycle of a compressed electro-spun fibroin mat.[2] This mode, provided a steady perturbed state can be sampled, the summation of multiple similar stages to provide superior statistics than would be possible by sampling a single cycle. The setup is shown in Figure 1A. At rest this poorly ordered system exhibits a limited number of very broad peaks but quite a high degree of chain folding.[3] With compression there is marked increase in the scattered intensity, both in the small (SAXS) and the wide (WAXS) angle regimes, as well a shift and reduction in broadness of the WAXS peaks (Figure 1B). We interpret the increase in the SAXS signal as an increase in scattering from grain boundaries and the WAXS as the formation of new crystalline domains. However, the limited number of very broad diffraction peaks make these data unsuitable for structural determination.

In order to provide an alternative, but complementary, perspective on the structural dynamics and the nature of the potential surface along which the polymer folds, during the piezo cycle we have turned to a computation approach. Density functional theory (DFT) calculations were performed within the framework of the projector augmented wave potentials parametrised by Perdew et al., [3] and the Tkatchenko-Scheffler correction [4] with a self-consistent screening to account for the weak correlations. Full structural optimisation of orthorhombic C₂₀O₈N₈H₃₂ was performed. The calculated lattice parameters (a = 9.409 Å, b = 6.984 Å, c = 9.221 Å) and the corresponding diffraction pattern (black vertical lines) are compared with the experimental data in Figure 1C.

Keywords: piezoelectricity; biopolymer; synchrotron wide angle X-ray scattering; millisecond resolved diffraction

The authors acknowledge beamtime on the SAXS/WAXS beamline at the Australian Synchrotron, part of ANSTO. The computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at National Supercomputer Centre (NSC) in Linköping, Sweden.

[1] Rockwood, D. N., Preda, R. C., Yücel, T., Wang, X., Lovett, M. L. & Kaplan, D. L. (2011). Nature Protocols 6, 1612.

[2] Sencadas, V., Garvey, C., Mudie, S., Kirkensgaard, J. J. K., Gouadec, G. & Hauser, S. (2019). Nano Energy 66, 104106.

[3] Perdew, J. P., Burke, K. & Ernzerhof, M. (1996). Physical Review Letters 77, 3865-3868.

[4] Tkatchenko, A. & Scheffler, M. (2009). Physical Review Letters 102, 073005.

High-throughput synthesis using inkjet printing allows the deposition of hundreds of nanoparticle compositions on a single substrate. It also introduces the challenge to characterize the phases and structures of these nanoparticles in an automated high-throughput way. Here, we develop a method to screen hundreds of nanoparticle combinations, collect the x-ray diffraction image, transfer the data to pair distribution functions and analyze the phase information. It has been successfully applied to characterize the phase compositions and atomic structures in an iron, nickel, cobalt nanoparticle array. Combining this method with inkjet printing and optical screening, it is possible to achieve the fully automated high-throughput searching for the optimal combinatorial nanoparticle catalysts.

Functional nanomaterials are frequently synthesized by the facile sol-gel method. In a broader sense, the process can be described as the conversion of molecular precursors in solution into inorganic solids via hydrolysis, condensation and aggregation [1]. It allows the targeted control of structural characteristics e.g. particle/crystallite size and polymorphism of a material. This is of particular importance for quantum materials, where the charge, spin, orbital and lattice are intrinsically coupled due to strong electronic interactions [1]. Since the sol-gel method is a non-equlibrium process, the synthesis of pure nanocrystalline samples is challenging if various stable and metastable phases exist, often leading to co-crystallization. Subtle changes in the synthesis parameters, such as temperature, pH and complexing agent, can strongly influence the resulting structural and physical properties of the materials. Despite this knowledge and the popularity of this synthesis method, studies on the parameters driving the crystallization process are rare and a deep understanding of the formation mechanisms is usually lacking.

The Bi₂O₃-Fe₂O₃ system is known to be challenging from a synthetic point of view, as sillenite-type Bi₂₅FeO₃₉, mullite-type Bi₂Fe₄O₉ and perovskite-type BiFeO₃ have a strong tendency to co-crystallize [3]. The target compound Bi₂Fe₄O₉ shows multiferroic behaviour close to room-temperature [4] and a spin liquid state just above the transition [5]. Its exotic magnetism materialises due to five competing magnetic exchange interactions involving two distinct Fe-sites, which drive antiferromagnetic coupling in the ab–plane and non-collinear ferromagnetic ordering along the c-axis [6]. Below a critical size of ~120 nm, size-dependent properties can be observed due to significant changes in the structural lattice [7].

In this study, we investigate how the synthesis parameters in a sol-gel approach affect the crystallization pathways and kinetics of Bi₂Fe₄O₉. We follow the transformation of molecular precursors into the fully crystalline structures using in situ total scattering and Pair Distribution Function (PDF) analysis with a second-scale time resolution. In total, five different precursors were synthesized using the respective metal nitrates and meso-erythritol as the complexing agent. The phases qualitatively appearing during crystallization as well as their transition and growth kinetics can be controlled by the synthesis medium and ratio of metal nitrate to complexing agent. More specifically, we observe multiple crystallization pathways including the initial formation of rhombohedral BiFeO₃ and subsequent transition into orthorhombic Bi₂Fe₄O₉, co-crystallization of BiFeO₃ and Bi₂Fe₄O₉, or the direct formation of Bi₂Fe₄O₉ from the precursor. During crystal growth, the lattice parameter b decreases significantly, although Bi₂Fe₄O₉ is known to exhibit positive thermal expansion [8] highlighting the influence of the crystallite size on the lattice. In addition, the overall crystallization process is predetermined very early in the synthesis process and mainly governed by the gel structures formed during evaporation of the solvent and organic components, as suggested by ex situ PDF analysis.

[1] Niederberger, M. (2007). Acc. Chem. Res. 40, 793. [2] Samarth, N. (2017). Nat. Mater. 16, 1068.

[3] Carvalho, T. T. & Tavares, P.B. (2008). Mater. Lett. 62, 3984.

[4] Singh, A. K., Kaushik, S. D, Kumar, B., Mishra, P. K., Venimadhav, A., Siruguri, V. & Patnaik, S. (2008). Appl. Phys. Lett. 92, 132910.

[5] Beauvois, K., Simonet, V., Petit, S., Robert, J., Bourdarot, F., Gospodinov, M., Mukhin, A. A., Ballou, R., Skumryev, V. & Ressouche, E. (2020). Phys. Rev. Lett. 124, 127202.

[6] Ressouche, E., Simonet, V., Canals, B., Gospodinov, M. & Skumryev, V. (2009). Phys. Rev. Lett. 103, 267204.

[7] Kirsch, A., Murshed, M. M., Litterst, F. J. & Gesing, Th. M.(2019). J. Phys. Chem. C 123, 3161.

[8] Murshed, M. M., Nénert, G., Burianek, M., Robben, L., Mühlberg, M., Schneider, H., Fischer, R. X. & Gesing, Th. M. (2013). J. Solid State Chem. 197, 370.

Keywords: Crystallization; Pair Distribution Function analysis; Phase transition; In situ total scattering; X-ray diffraction; Synthesis

“Funded by the Deutsche Forschungsgemeinschaft (DFG – German Research Foundation), project number 429360100”

The local structures of four citric acid cross linked cyclodextrin nanosponges (CD); goethite (CDG), hydroxyapatite (CDHA) and goethite/hydroxyapatite (CDGHA) functionalized cyclodextrin nanosponges, prepared by ultrasound-assisted polycondensation polymerization, was studied the using atomic pair distribution function (PDF) technique. The PDFs were analyzed by comparing experimentally determined PDFs from samples under study and those from known control samples and the overall structural information extracted through visual inspections of PDFs. The samples do show the feature of cyclodextrin network linked by citric acid, with strong sharp peaks in the low-r region and weak broader peaks in the mediate and high-r region. CD and CDHA show the feature of polymer cyclodextrin, since there is only noise and density modulation after 13 Å in their PDFs, while the CDG and CDGHA show the feature of crystallinity (signal even after 13 Å), which is approximately the largest atomic distance in cyclodextrin. The short-range order, which is the spacing of neighbor glucose and glucose connected by citric acid networks, is similar for all samples despite their difference in crystallization. CD and CDHA have quite similar cyclodextrin network according to their similarity in PDF while CDG and CDGHA also have cyclodextrin network but contains crystalline goethite.

Although amorphous materials lack long-range translation order, they are strongly ordered at the length scale of single interatomic bonds, and retain some order into more distant coordination shells. One form of order is local, approximate rotational symmetry. For example, local five-fold rotational symmetry has been shown in simulations to correlate to slower dynamics in metallic liquids and greater strength in metallic glasses [1]. Local structural symmetry gives rise to symmetry in electron nanodiffraction speckle patterns acquired with sub-nanometer probes, but evaluating symmetries in patterns from amorphous materials is challenging. Only small clusters of atoms have symmetry, their symmetry is often distorted or imperfect, and the symmetric cluster is embedded in more atoms which are disordered. One method to assess symmetries in nanodiffraction is the angular power spectrum. We have used angular power spectrum data to demonstrate that Zr₆₅Cu_27.5Al_7.5 glasses exhibit increasing 4-fold and 5-fold structural symmetry with increasing stability in the glassy state and increasing hardness [2].

However, angular symmetry is subject to three artifacts that give rise to power that does not correspond to symmetries in the structure. First, aliasing transfers power from lower n to higher n. Second, electron nanodiffraction patterns without Friedel symmetry give rise to non-structural odd-order power. Third, the extra atoms surrounding the ordered cluster can create speckles which cause the power in rotational orders that are not present in the structure. We have proposed a different method to assess symmetries in amorphous nanodiffraction inspired by the Symmetry STEM method for crystals [3]. This method defines symmetry coefficients S_n which sample only the discrete angles associated with n-fold symmetry [4]. The discrete sampling avoids the aliasing and Friedel breakdown artifacts entirely, and it reduces the incidence of the structure overlap artifact. Electron scattering simulations in Figure 1(a) show that S_n is sensitive to nearest-neighbour icosahedral order in metallic glass atomic models. Experiments on Pd₄₃Ni₁₀Cu₂₇P₂₀ in Figure 1(b) result in symmetries consistent with dodecahedral structure found in previous studies.

Figure 1(c) demonstrates the use of symmetry coefficients for spatial mapping of high-symmetry clusters. It is derived from a 4D STEM data set acquired with a high sensitivity, high-speed direct electron detection camera recently developed by the Wisconsin Materials Research Science and Engineering Center and Direct Electron, Inc. These data were acquired at 7,000 frames per second (fps). The current maximum speed of the camera is 24,000 fps, and the ultimate design speed is in excess of 100,000 fps. These extremely high speed will enable time-resolved, in situ experiments using symmetry coefficients to track the evolution of local symmetries in supercooled liquids as they cool through the glass transition.

[1] Cheng, Y. Q. Q., Ma, E. (2011) Prog. Mater. Sci. 56, 379.

[2] Muley, S. V., Cao, C., Chatterjee, D., Francis, C., Lu, F. P., Ediger, M. D., Perepezko, J. H., Voyles, P. M. (2021). Phys. Rev. Mater. 5, 033602.

[3] Krajnak, M. & Etheridge, J. A (2020) Proc. Natl. Acad. Sci. 117, 27805.

[4] Shuoyuan, H., Francis, C., Ketkaew J., Schroers J., Voyles P. M. (in preparation)

The pair-distribution function (PDF) method is widely used to obtain structural information beyond the typical diffraction techniques together with standard structure refinement utilizing Bragg reflections [1]. PDF analysis using x-ray and neutron powder diffraction data is well established. Electron-based PDF (ePDF) analysis has drawn considerable attention in recent years [2,3,4]. In addition to the very strong electron-matter interaction (~10⁵ than x-ray), the main advantages of the electron-based over x-ray and neutron-based is to utilize modern electron microscopes, which offer (sub)nano-sized probe of the electron beam and various imaging and spectroscopy techniques simultaneously. Therefore, ePDF is particularly good for study nano-materials, disordered materials and specific region of interest in the specimens.

Although the procedures of ePDF analysis is similar to those obtained by x-ray and neutron, several parameters and steps, which are due to electron scattering and TEM practice, are crucial in the processing. For instance, Q_max is always important in all PDF experiments. However, Q_min, which is not considered in x-ray and neutron, should be carefully determined in ePDF. On the other hand, the shape factor can influence the ePDF results. The smaller the particles the stronger effect can be seen. Different stepwise atomic layer arrangement of the crystal surface can contribute significantly in the analysis [5]. In addition to experimental and analysis procedures different to those for x-ray or neutron-based, the uniqueness and possibility of ePDF analyses of some amorphous materials and nanostructures will be discussed.

[1] Egami, T. & Billinge, S. J. L. (2002). Underneath the Bragg Peaks: Structural Analysis of Complex Materials. Amsterdam: Elsevier Science.

[2] Abeykoon, M., Malliakas, C. D., Juhás, D., Božin, E. S., Kanatzidis, M. G. & Billinge, S. J. L. (2012). Z. Kristallogr. 227 248.

[3] Tran, D.-T., Svensson, G. & Tai, C.-W. (2017). J. Appl. Crystallogr. 50, 304.

[4] Gorelik, T. E., Neder, R., Terban, M. W., Lee, Z., Mu, X., Jung, C., Jacob T. & Kaiser, U. (2019). Acta Crystallogr. B 75, 532.

[5] Tran, D.-T., Svensson, G. & Tai, C.-W. (2016). arXiv:1602.08078.

The Knut and Alice Wallenberg (KAW) Foundation is acknowledged for providing the electron microscopy facilities and financial support under the project 3DEM-NATUR for the initial development. Swedish Research Council (project no. 2018-05260) is also acknowledged.

Correlated disorder is any type of deviation from the average crystal structure that is correlated over the range of a few unit cells only. As correlated disorder lies at the origin of the physical properties of a compound, many open questions in materials science are related to it. Unfortunately, the diffuse scattering analysis from single-crystal X-ray and neutron diffraction needs large crystals which are often not available. In the case of submicron sized crystals, pair distribution function analysis on powder samples could be applied. However, as an alternative we suggest to turn to single-crystal electron diffraction. While the quantitative analysis of diffuse X-ray and neutron scattering has already been done for different types of correlated disorder, we will present for the first time the quantitative analysis of diffuse electron scattering using an evolutionary algorithm in DISCUS [1].

In the electron diffraction patterns of Li_1.2 Ni_0.13Mn_0.54Co_0.13O₂ diffuse streaks are present, which are caused by stacking faults (i.e. variations in the stacking of subsequent Li-, O- and transition metal -layers). An evolutionary refinement algorithm in DISCUS was used to determine the stacking fault probability as well as the twin ratio in Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ by a refinement of the intensity profile of the diffuse streaks_. The refinement algorithm was first tested on simulated data, after which it was applied to experimental electron diffraction data obtained by three-dimensional electron diffraction (3D ED).

Funding information

The research leading to these results has received funding from the Research Foundation Flanders (FWO Vlaanderen) (grant No. G035619N)

[1] Proffen, T., & Neder, R. B. (1997). J. Appl. Crystallogr. 30, 171-175.

Metal-organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X-ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high-throughput approach for structural analysis of MOF nano- and sub-microcrystals by three-dimensional electron diffraction (3DED). A new zeolitic-imidazolate framework (ZIF), denoted ZIF-EC1, was first discovered in a trace amount during the study of a known ZIF-CO₃-1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF-EC1 has a dense 3D framework structure, which is built by linking mono- and bi-nuclear Zn clusters and 2-methylimidazolates (mIm^-). The discovery of this new MOF highlights the power of 3DED in developing new materials.

In recent years, Electron Diffraction, and especially the 4D-STEM [2] is growingly becoming a routine part of structural characterizations of materials at the nano-scale. Its un-matched spatial resolution (down to sub-nm) enables the exploration of local variations within a sample, which alternatively is averaged over the entire irradiated sampled area, when explored, for example, by x-rays. As often shown in electron microscope, samples are often heterogeneous, and consequently their local properties, which then reflect on the average behavior of the material, composite, or device. Besides morphology and composition, the local structural order can vary, especially in evolving systems. In this study, we explore how far we can take electron diffraction when the interest is in the evolution of materials.

We challenge ourselves with mapping the local structure in a composite of crystalline Ni and amorphous Zr-Cu-Ni-Al Bulk Metallic Glass (BMG) that was fused into a composite via hot-rolling [2]. Using a fast camera looking through the fluorescence screen, we captured diffraction patterns in a 4D-STEM modality, where we captured diffraction patterns coupled with beam precession with 3 nm step size in a Ni/BMG/Ni cross-section sample that was cut from the composite - in total 131x289 diffraction patterns. Using the collected diffraction patterns and tailoring automated data reduction and analysis pipelines, such as auto-masking, azimuthal-integration, Fourier-transformation to get the electron Pair Distribution Function (ePDF) and various fittings of the PDF, we were efficiently deriving a large set of physically meaningful scalars, which we generalize as Quantities of Interest, or QoI of a scanning nano-structure electron microscopy (SNEM).

Using different QoI's (see Figure)- those derived directly from the images, such as virtual-dark-field and mostly from ePDF's, we could map out most clearly Ni/BMG boundaries, visualize inter-diffusion between Ni and BMG, extract regions of formed nano-crystals within the BMG, follow compositional changes via the average bond-distance (verified with EELS from the same area) and extract the distribution of atomic pairs. We were also able to map the deviation of each pixel within the BMG from an expected structural model, which exposed the BMG/Ni inter-diffusion front. Finally, we could estimate the effective local structure of the nano-crystalline inclusions within the BMG as FCC structures.

Using an assembly of these results we could learn that nano-crystalline inclusions within the BMG are located in regions where Cu is deficient and Zr is in excess. Most importantly, we learn the origin of success in forming the Ni/BMG composite via hot-rolling, which is nonetheless, a challenging goal. Hot rolling is found to be a challenging process due to the excessive formation of nano-crystallites at the Ni/BMG interface. Here, however, the assembly of SNEM results suggested that the metallic Ni amorphized instead of the BMG--Ni crystallize at the BMG/Ni interface. These results emphasize the richness SNEM experiments hide, and with the assistance of automated (and in the future - autonomated) pipelines can expose the story of evolving systems.

[1] Xiaoke Mu, Andrey Mazilkin, Christian Sprau, Alexander Colsmann, Christian Kübel, (2019). Microscopy. 3554, 301
[2] Sina Shahrezaei, Douglas C. Hofmann, Suveen N. Mathaudhu (2019). JOM. 71, 2

An information theory based method [1,2] for the classification of more or less 2D periodic images from real-world crystals with atomic resolution [3] into non-disjoint plane symmetry groups is briefly described and applied to three pairs of synthetic images. One image of these three pairs is free of noise by design. Gaussian noise of mean zero has been added to the other three images of these pairs. All three image pairs are also highly pseudo-symmetric so that it is, for human beings on the basis of a visual inspection alone, very difficult to identify the underlying plane symmetry of the noisy image correctly. This is because all genuine symmetries and pseudo-symmetries are broken by the added noise so that their differences are diminished. The new information theory based classification method, on the other hand, overcomes such challenges [4].

The method enables the objective, i.e. researcher independent, identification of the plane symmetry group that provides the best known separation of structure and generalized noise at the given noise level of a processed image. This identification enables the most meaningful averaging of the image in the spatial frequency domain in support of subsequent crystallographic analyses. This kind of averaging is over all correctly identified asymmetric units in the image and removes noise more effectively than traditional Fourier filtering. Ratios of numerically obtained geometric Akaike Information Criterion values, i.e. first-order geometric-bias corrected sums of squared residuals between the complex-valued Fourier coefficients of the raw image intensity and their counterparts from the applicable symmetry models of this data, are utilized for plane symmetry classifications within the appropriate symmetry hierarchy branch or intersecting branches. The symmetrized model of the noisy raw data that is the best representation of the 2D periodic structure in the Kullback-Leibler divergence sense will be found within such a single branch or at the crossing with other such branches in cases of more elaborate symmetries.

Numerically obtained confidence levels are assigned to the classification of noisy images into minimal supergroups over their translationengleiche maximal subgroups. The resulting plane symmetry classifications are always generalized noise level dependent, which allows for better classification results as noise decreases with future improvements to the imaging and image-processing procedures. The information theory based method delivers only probabilistic classifications as it is fundamentally unsound to assign an abstract mathematical concept, such as a plane symmetry group, with 100 % certainty to the record of a noisy real-world imaging experiment of an imperfect real-world crystal.

[1] P. Moeck, Symmetry 10, paper 133 (46 pages) (2018), open access, DOI: 10.3390/sym10050133

[2] P. Moeck, IEEE Transactions on Nanotechnology 18, 1166-1173 (2019), DOI: 10.1109/TNANO.2019.2946597, see also http://arxiv.org/abs/1902.04155, August 31, 2019 for an expanded version of this review

[3] P. Moeck, A. Dempsey, and C. Shu, Microscopy and Microanalysis 25 (Suppl. 2), 184–185 (2019), DOI: 10.1017/S143192761900165X

[4] P. Moeck and A. Dempsey, Microscopy and Microanalysis 25 (Suppl. 2), 1936–1937 (2019), DOI: 10.1017/S1431927619010419

The presented Virtual X-ray Laboratories (v-XRLab) have been developed to address the lack of advanced and expensive research equipment for educational purposes, facilitate hands-on practice associated with online science or engineering courses, and enhance students’ knowledge of equipment design and operational principles. Also, in contrast with fully computerized contemporary X-ray equipment, the v-XRLabs help students understand factors affecting data accuracy and method limitations first-hand, and, consequently, better estimate reliability of the experiment results.

During the COVID-19 pandemic, the virtual labs helped instructors minimize drawbacks of lost access to actual physical laboratories.

Integrated cloud-based virtual laboratories (ATeL’s v-Labs) allowed learners to perform authentic research and laboratory experiments online, using highly accurate digital copy of a multifunctional X-Ray Powder Diffractometer (v-XRPD) and X-ray Fluorescence (v-XRF) spectrometer. The v-XRPD realistically imitates the design and operation of a typical flat plate geometry diffractometer, and it also includes educational analytical software.

The v-XRLab includes an open repository of samples available for experiments. The-Diffractometer can work with CIF files obtained from the CCDC CSD, XY formats produced by a vendor's instrument, and some other plain text files as well. The open collection of virtual samples available for online experimentation includes alloys, ceramics, polymers, nanostructured materials, thin films, and even human kidney stones.

Experimental data can be collected and handled manually or automatically. Virtual data can be exported to popular software as well.

The v-XRLabs incorporate self-guided online experiments that couple hands-on practice with efficient contextual ‘just-in-time learning” by integrating simulations with video and voice instructions, manuals, quizzes, references, and other multimedia learning resources. This combines skill development, knowledge acquisition and performance-based assessment into a single process.

A complimentary authoring tool enables instructors to modify existing online experiments and to create new ones, as well as to add new samples in the repository. New samples can be either based on actual XRD patterns or be calculated from known structural data.

The v-XRLabs incorporate an augmented reality (AR) X-Ray diffractometer (AR-XRPD) and its attachments running on a mobile device or smart glasses and synchronized in real time with the main simulated XRPD and the relevant processes. This dramatically enhances student engagement and provides them with unique opportunities for data analysis and deeper exploration of the equipment and processes in augmented reality.

The v-XRLlabs were incorporated into courses on chemistry, materials science, forensics, mineralogy, metallurgy, and materials characterization techniques, among others. They has been used as follows: (i) as the only tool for lab practice on the relevant subjects, by the students who have no access to real equipment including MOOC students; (ii) for hybrid experimentation in combination with equipment; (iii) for preparing students and tech personnel to effective and meaningful hands-on practice in actual X-ray labs; (iv) for performance-based assessment of students’ and trainees understanding, and their ability to apply acquired knowledge and skills for performing experiments, and solving practical tasks; (v) and for lecture demonstrations.

The presenters will share their experience in using the v-XRLabs during the COVID-19 pandemic and beyond it. The v-XRLab can be accessed at the following link: https://atelearning.com/XRLab/index.php

Crystal structures of proteins are three-dimensional, but most depictions of them, in textbooks and in the scientific literature, are not. When students are on campus, they can interact with physical models, discuss structures in the computer lab and experience the properties and functions of proteins in the biochemistry lab. We describe two projects that support interactive, collaborative and experiential learning in a remote setting. In the first project, students explored metabolic enzymes using the visualization software Pymol. Starting with crystal structures in the Protein Data Bank, students learned the basics of Pymol: they superimposed structures representing different stages in the catalytic mechanism, highlighted non-covalent interactions, identified bonds broken and made, and discussed the active sites of these enzymes in the context of the protein fold. In weekly meetings, students shared their progress and setbacks amongst each other, and used peer-to-peer learning to elevate their chemical and graphical design skills. Individually, they created different scenes and made them into a short video for which they provided an explanatory voiceover. Students wrote about their progress in weekly reflections. Many students reported being “excited and challenged” about learning a new technique at the outset. Later, deeper learning strategies emerged such as searching the primary literature or comparing existing videos to see how one might position an active site. The help-seeking behavior also became more sophisticated, for example asking for a video tutorial showing how to add or remove functional groups from a model. Overall, students were actively engaged in their projects and were eager to share what they had learned in discussions with their peers. The second project, housed on the public science site Proteopedia.org, aims at presenting examples of conformational change in a more interactive way. We wrote a series of Jmol scripts (storymorph.spt) to make it easier to superimpose structures and create morphs (fictional trajectories connecting conformational states). Using an algorithm that combines rigid-body movement with linear interpolation, morphs are made on the fly, allowing the visitor to change parameters (such as the timing of distinct parts of the conformational change or the initial superposition) to get a better feel for how the conformation might change. It is also possible to slow down or pause the morph, allowing visitors to explore the suggested intermediates in three-dimensions, including potential clashes or unrealistic bond lengths or angles. Morphs made available through this project include hexokinase binding to glucose, RNA polymerase transitioning from early to late initiation, conformational changes in calmodulin, and the pre-fusion to post-fusion transition of the coronavirus spike protein. Together these two projects highlight simple ways to keep science-learning interactive, collaborative, fun, and — most importantly — three-dimensional in spite of the limitations caused by a pandemic.

Many months of this pandemic brought high concentration on online teaching in basically all levels of education. Of course, the least problematic is such teaching in universities where many things can be transferred to online form without significant losses and in certain cases even with some benefits. Of course, not for the work that should teach students some manual skills. Otherwise, there are no limits for interactive communication during the online teaching. However, it may be easier for the teachers rather than for students who must sit at the computer many hours a day. Universities are supporting different platforms for online teaching. While for organizing of meetings I prefer to use Zoom or similar platforms, for teaching I have decided to prepare everything in MS Teams in the form for education where it is easy to create a team for the subject and assign students from the list of university students.

Our faculty required that all the presentations be recorded, and the records are available, in addition to presentations (ppt, pdf), to all relevant students till the end of semester. Some shared files like Excel or Word ones have possibility of multiple access of teacher and student. Probably the most useful part is Notebook that can contain different folders owned by teacher only, shared for all and owned by each individual student, respectively. In the shared folder, anybody can write formatted text, draw, insert pictures, tables directly in Teams or in One Note application with a few more advanced features. Students cannot see folders and pages of other students while the teacher can see everything. So, the teacher can easily click on the corresponding place of any student any time and see up-to-date information, e.g. where the student is during his/her task. Teacher can also write or draw directly to their documents. Usually, it is working quite quickly if the Internet is not too slow. The system was used for online teaching of fundamentals of crystallography and X-ray diffraction for smaller groups of students up to 10. In addition to simple examples and tests, graphical possibilities were used either with mouse or graphical tablet. The students had different symmetrical periodical 2D patterns with a task to draw elementary cell, corresponding symmetry elements, and determine the plane group from the list. In order, to make their life easier, they could use a portfolio of all symbols and it was then sufficient to move specific symbols to relevant positions. A similar way was used for space groups (complete diagrams of general positions with symmetry elements or vice versa complete diagrams of symmetry elements with general positions, the determination or estimation of the space group). The work was quite smooth.

A little more complicated was the preparation of online practical courses when the entrance of students to the faculty building was completely forbidden. One was the basic problem of powder diffraction – determination of lattice parameter of unknown cubic phase and then also phase analysis of mixture of 3-6 phases. This practical part always begins with a short excursion in X-ray laboratory showing them a few instruments, description of powder diffractometer, preparation of different samples, specimen alignment and automatic measurement in symmetrical scan. So, everything was recorded to videos and what was only missing for students was their own specimen preparation. This is followed by demonstration of fast evaluation of powder pattern and generation of a file with peak parameters. The students used the free program Winplotr. A short video tutorial how to use it quickly for simple fitting of XRD peaks was provided. Students used this output (each with different dataset) to index peaks according to procedure described on web link and determined the lattice parameter considering the instrumental aberrations. This was done in Excel file simultaneously accessible also by the teacher. The first part was closed by looking into the ICDD Powder Diffraction File and trial to find the phase (demo by the teacher). Usually, it was not found because the lattice parameter deviated from the database value from some reason that was discussed. Then the pattern of a mixture of phases was evaluated in commercial software (demo by the teacher), the list of peaks was generated (2q, d, I) and the students obtained scanned education edition (ICDD material) of Hanawalt index and made the search “manually”, again with different datasets. Interaction of the teacher was necessary. Finally, for homework, the students should download 30-days trial of program Match and use it for the phase analysis of the mixture (again a short video tutorial provided. More online “practical” tasks were prepared, for example study of textures and stresses in thin films showing different diffraction geometries and scans.

Real examinations could be realized after the winter semester in February 2021. In general, I have never heard so well-structured and correct answers. I think that the reasons were the following. Students had everything available in their Teams folders. Each student had to go through all the tasks and materials independently but except the direct online teaching in any time that was suitable for him/her, and I did the same. The students could return to some parts of presentations and if something were not clear, they could look at corresponding video part. So, my overall experience was positive.

However, the courses were for smaller groups of students and do not require any manual skills, so they can be adopted quite easily for online form.

In order to address the loss of crystallographic training opportunities resulting from the cancellation of conventional schools around the world due to the COVID-19 pandemic we have started an online crystallography school with live lectures and live Q&A using Zoom Webinar. In 2020 we ran three versions of the school: two 10 one-hour classes on basic topics in crystallography and five 1.5-hour classes on advanced topics. In June 2021 we plan to run a fourth school consisting of 10 1.5 hour classes on advanced topics. We have reported on the execution and results of the two basic schools held in 2020 previously (1).

For the June 2021 school, we have scheduled ten 1.5 hour lectures on advanced topics including: electron diffraction, refinement, twinning, powder and PDF analysis, solution scattering and macromolecular crystallography, non-spherical atom refinement and charge density analysis, and data mining.

This presentation will review the execution and outcomes of the December 2020 and June 2021 advanced topics schools.

1. https://doi.org/10.1063/4.0000078

My objective is to share approaches by which I incorporate structural biology into our biochemistry curriculum at Hampton University. I will also discuss methods to engage K-12 and undergraduate students in crystallographic research and structural biology (since 2001). I will show the successes and failures involved in the process of fully integrating these pre-baccalaureate students in crystallography research. Our outreach efforts have included socioeconomically underserved students or groups underrepresented in STEM. We will present strategies for recruiting and retaining STEM students. We will present the significant barriers to our research programs. We will also discuss potential funding sources. Finally, we will present how structural science has helped COVID-proof our research and biochemistry teaching approach over the past year of remote-learning.

An approach for increasing the impact of undergraduate scientific training with a discovery based X-ray structure determination lab module has been part of the chemistry curriculum at Vassar College since 2010. Just as chemical crystallography and complimentary spectroscopic techniques such as NMR can be fast, effective tools to experimentally determine the structure of molecules and enhance students learning of molecular structure, they can also provide an inspiring opportunity for students to write short, scientific journal style reports that can be edited and published in collaboration with a mentor. This talk will briefly review the X-ray crystallography module and then focus on the experience of conducting this module with remote and hybrid online learning during the pandemic.

Open slot

https://pdfitc.org/

https://www.diffpy.org/products/diffpycmi/index.html

https://www.cryst.ehu.es/

Self-organization is a key tool for the construction of functional nanomaterials. We have recently established a novel method for the self-organization of biomolecular building blocks and nanoparticles. Towards this goal, protein containers, engineered with opposite surface charge, are used as an atomically precise ligand shell for the assembly of inorganic nanoparticles.[1] The assembly of these protein-nanoparticle composites yields highly ordered nanoparticle superlattices with unprecedented precision. The structure of the protein scaffold can be tuned with external stimuli such as metal ion concentration.[2] Importantly, these composite materials show catalytic activity inside the porous material.[3] Along these lines, the protein containers used as a scaffold offer a viable route towards renewable materials.[4]

For the formation of biohybrid materials, the inorganic cargo has to be encapsulated into the protein containers. Here, we demonstrate that the highly specific cargo-loading mechanism of the bacterial nanocompartment encapsulin can be employed for encapsulation of artificial cargo such as inorganic nanoparticles.[5] For this purpose, gold nanoparticles were decorated with cargo-loading peptides. By lock-and-key interaction between the peptides and the peptide-binding pockets on the inner container surface, the nanoparticles are encapsulated with extremely high efficiency. Most notably, the supramolecular peptide binding is independent from external factors such as ionic strength.[5] Cargo-loading peptides may serve as generally applicable tool for efficient and specific encapsulation of cargo molecules into a protein compartment. Moreover, these nanoparticle protein-container composites are suitable for applications as building blocks in materials, exploiting the plasmonic properties of gold nanoparticles for light manipulation or sensing.

[1] M. Künzle, T. Eckert, T. Beck, J. Am. Chem. Soc. 2016, 138, 12731-12734.
[2] M. Künzle, T. Eckert, T. Beck, Inorg. Chem. 2018, 57, 13431-13436.
[3] M. Lach, M. Künzle, T. Beck, Chem. Eur. J. 2017, 23, 17482-17486.
[4] a) M. Künzle, M. Lach, T. Beck, Dalton Transactions 2018, 47, 10382-10387; b) M. Lach, M. Künzle, T. Beck, Biochemistry 2019, 58, 140-141.
[5] M. Künzle, J. Mangler, M. Lach, T. Beck, Nanoscale 2018, 10, 22917-22926.

In recent years, the genome of microorganisms from various habitats, such as industrial
waste areas, areas rich in vegetable oils or in soils contaminated with oil, has been
analyzed. This has allowed us to identify enzymes with functions that offer enormous
potential for various applications in the industrial sector, from catalysis to remediation.
Much of this knowledge has been leveled by bacteria of the genus Pseudomonas, since their
metabolic versatility has been involved in a large number of biotechnological applications.
Lipases catalyze the hydrolysis of triacylglycerides whose products are fatty acids and
glycerol. These enzymes have a catalytic triad consisting of a serine, an acid residue
(glutamic acid or aspartic acid) and a histidine. In addition, lipases have a preserved
structure known as a lid. This lid is a mobile element that discovers the active site.
It has been observed that lipase 2 (lip2) of Pseudomonas alcaligenes has a sequence
identity of 48% with the lipase of P. aeruginosa, while the region of the lid has high
identity with lids described in other halophilic or psychrophilic bacteria such as
Marinobacter mobilis, Oleiphilus messinensis, Oleispira antartica or Hahellaceae
bacterium, which makes it different from other lipases described until now.
The lip 2 gene of P. alcaligenes was cloned into the Pet 28a vector and was expressed in
Escherichia coli BL21 cells in order to obtain a crystallographic structure that allows us to
describe and characterize the possible structural changes of the enzyme, as well as the
possible implications of these changes in the stability and catalysis of lip 2 of P.
alcaligenes.

Structural and functional studies of key enzyme (LpxC (UDP-3-O-acyl-N-acetylglucosamine deacetylase) from salmonella typhi involved in Gram-negative bacterial lipid A biosynthesis

Sudhir Kumar Pal¹, Sanjit Kumar^1*

¹ Centre for Bio Separation Technology, VIT University, Katpadi, Vellore, Tamil Nadu-632014

Abstract

Over the last decade, in the case of gram-negative bacteria the frequency of antibacterial resistance especially in ill and hospitalized patients (including multidrug resistance (MDR) and its association with severe infectious diseases) has increased at alarming rates. Salmonella typhi (gram negative bacteria) is an ubiquitous pathogen responsible for a number of diseases such as pneumonia, meningitis, etc. The increasing number of infections caused by MDR Salmonella typhi must be re-explored for novel treatment strategies. LpxC, a metal dependent amidase (highly active in the presence of Zn2+ ions (Kd ~60 pM)) is one such vital and rate-limiting enzyme committing the step of Lipid A (a strong human immuno-modulator bacterial endotoxin) biosynthesis. Many structures of LpxC enzyme in complex with different inhibitors are solved by various structural biology techniques but most of these inhibitors have been reported to have poor anti-microbial activity. Compounds with indole-2-carboxamide scaffold in their skeleton display various biological activities including anti-bacterial activity. We have done indole-2-carboxamide scaffold-based virtual screening and observed inhibitors like 0435 (-9.0 kcal/mol), 0436 (-9 kcal/mol), 1812 (-8.6 kcal/mol), 2584 (-8.5 kcal/mol), and 2545 (-8.4 kcal/mol) bound to the functional active site of LpxC.

β-Lactoglobulin (BLG) is a protein from the lipocalin family [1]. BLG is a milk protein with a natural affinity to fatty acids and retinol [2], however, it can bind with relatively high affinity but rather low selectivity a variety of biomolecules [3]. A conserved structural element of lipocalins is the eight-stranded antiparallel β-barrel which is the primary binding site for ligands [4]. Like many proteins from the lipocalin family, BLG can be modified by rational site-directed mutagenesis. Substitutions in the region of the β-barrel can be used to re-design the shape of the binding pocket to create new BLG variants with specific ligand preferences [5]. New variants (mutants) of β-lactoglobulin with increased affinity for tri-cyclic drugs (e.g. antipsychotics and antidepressants) may be used in the future as molecular transporters that selectively recognize and remove toxic compounds from the body.

New BLG mutants with substitutions at positions 39, 56, 58, 71, 92, 105, and 107 were expressed in E.coli. All proteins were purified by anion exchange and size-exclusion chromatography. Crystals were obtained by the vapor diffusion method in the hanging drop setup. New BLG mutants, possessing the different shape of the binding pocket, were co-crystalized with tricyclic drugs (e.g. fluphenazine, clomipramine, and chlorpromazine) and selected fatty acids. X-ray diffraction data were collected at XtaLAB Synergy (Rigaku). Structures of BLG‑ligand complexes (2.5-1.5Å) were solved by molecular replacement. Determined crystal structures revealed that some substitutions reduced the length of the binding pocket preventing fatty acids from binding at this site. Crystallographic studies were supported by biophysical studies (circular dichroism) which allowed to determine the binding constant for selected protein-ligand complexes.

Advances in computational protein design have allowed for the development of new proteins with unique properties. Symmetric designer proteins have remarkable stability and can serve as versatile building blocks for the creation of macromolecular assemblies. Here we present the development and structural determination of SAKe: A new symmetric, stable protein building block with modifiable loops. Following the observation of pH induced 3D self-assembly, we engineered metal binding sites along the protein's internal rotational axis to fabricate 2D surface arrays. Using atomic force microscopy, we demonstrated Cu(II) dependent on-surface 2D self-assembly. Additionally, using dynamic light scattering and x-ray diffraction, we identified and characterized a SAKe mutant which shows in solution Zn(II) mediated nanocage formation. This work showcases a stable and highly modifiable SAKe protein scaffold, which holds promise as a building block for the creation of multi-functional macromolecular materials.

Serial crystallography has made remarkable progress since its origin. The advantages of serial crystallography cover the aspects of room-temperature structure determination of the biomacromolecules, micron or sub-micron sized crystal structure determination, as well as time-resolved research. Sample delivery system is one of the key parts of serial crystallography. It is the main limiting factor affecting the application of serial crystallography. In the existing sample delivery technologies, the samples are usually delivered in linear motion. Here we show that the samples can be also delivered using circular motion, which is a novel motion mode never tested before. We report a microfluidic rotating-target sample delivery device, which is characterized by the circular motion of the samples, and verify the performance of the device on the synchrotron radiation facility [1]. The microfluidic rotating-target sample delivery device consists of two parts: a microfluidic sample plate and a motion control system. Sample delivery is realized by rotating the microfluidic sample plate containing in-situ grown crystals as shown in Fig. 1. This device offers significant advantages, including a very wide adjustable range of delivery speed, low background noise, and low sample consumption. Using the microfluidic rotating-target device, we carried out in-situ serial crystallography experiments with lysozyme and proteinase K as model samples on the Shanghai Synchrotron Radiation Facility, and performed the structural determination based on the serial crystallographic data. The results showed that the designed device is fully compatible with the synchrotron radiation facility, and the structure determination of proteins is successful using the serial crystallographic data obtained with the device.

New "dynamic theory of protein crystallization (DTPC)" considers protein crystallization as a competitive process between different “protein-protein adhesion modes (PPAM)” mutually incompatible in molecular stacking into the crystal lattice. Large surface of protein molecules offers variety of different adhesion modes and only some of them are compatible in a single crystal form. The DTPC searches for the crystallization conditions supporting spontaneous preference of a dominant protein-protein adhesion mode and suppression of all adverse adhesion modes in the newly formed solid phase. The DTPC is based on the concept of PPAM giving us tools for manipulation with protein adhesion and allowing the intuitive design of experiment to increase the number of crystallizable proteins, to choose rationally the desired polymorph form and to increase the resolution of protein structures. The necessary condition for formation of single crystal is its growth according to the „principle of the dominant adhesion mode (PDAM)". It provides non-conflicting explanation for all available experimental observations regarding the protein crystallization and also for catalysis of crystal growth on heterogeneous substrates [1]. In a very simplified form, the necessary condition for the successful crystal growth can be written as a high difference of free energies of the competitive processes ΔF_cryst ~ F_{dominant AM} - Σ F_{incompatible AM}

This offers the experimenter a rational way to grow diffraction quality crystals and also to select the required crystalline form. The new approach changes the situation significantly and leads to enhancement of efficiency and accuracy of all standing crystallization methods. DTPC with PDAM are general and should be strictly respected by any method of protein crystallization.

Heterogeneous crystallization. Historically, there were different explanations why some heterogeneous materials initiate protein crystallization. Here, we propose the universal explanation why some materials are suitable for crystal initiation and other not. The DTPC explains efficiency of crystallization catalyzers (e.g. bioglass, coarsely wrinkled foils, nano-carbon materials, imprinted polymers, porous Si, hoarse hairs, properly coated nanotubes and nanostructured carbon black [1]) as follows. The specific adhesion in depressions in the substrate surface leads to identical orientation of protein molecules. Thus, it restricts an access to their adhesive surfaces responsible for incompatible PPAM. It enforces a unique PPAM in the growing crystal nuclei. They are more stable because of lower number of stacking faults. Therefore, they do not dissolve and can continue to grow even after being released into the seemingly under-saturated bulk solution. Contrary to a number former mutually contradicting explanation, this explains all available experiments on a unique common basis. By active control of crystallization process in slightly under-saturated conditions, one can rationally limit crystal formation to cavities only. The new insight promises better design of natural and artificially prepared crystallization catalyzers promising an increase in a number of crystallizable proteins and higher resolution in structure determination.

Homogeneous crystallization. Also here, one should look for the systems providing the highest difference between free energies of mutually exclusive protein-protein adhesion modes. The temporary molecular clusters formed in the overcrowded crystallization solution play here an important role. The adhesion properties of the protein molecule in these complexes may differ radically from the adhesion properties of the original molecule. If the crystallographer knows the rules for the formation of these temporary complexes, he can control preferences of the adhesion modes active in the emerging crystal. He can decide which of the mutually exclusive protein-protein adhesion modes succeeds and becomes dominant by using his knowledge of the adhesion modes between the target protein and the „protein-surface-active molecules (PSAM)“. Very reach and natural source of the adhesion mode examples is the PDB offering a deep inshight how the „protein surface shielding agents“ work in practice and how the „crystal structure forming elements“ help in finding the best crystal architecture [2]. If the crystallographer fails in suppressing the mutually incompatible adhesion modes, the result cannot be quality crystal. Thus even very good precipitation agent can be a bad crystallization agent, if it does not differentiate among adhesion modes of the target protein.

Classical theories of protein crystallization and majority of papers on protein crystallography concentrated in last decades to an efficient and rapid precipitation. Low attention was given to reasons why the growing solid phase is regular and to the fact that protein crystallization is a competitive process between different adhesion modes. The abstract notion “adhesion mode” introduced by the DTPC gives the experimenter new tools controlling the crystallization and increasing predictability in protein crystallization methods.

[1] Yau S.T. et al, Nature 406, 494 (2000); Chayen, N.E., et al, J. Mol. Biol. 312, 591 (2001); Redecke L. et al. Nature Methods 9, 259 (2012); Khurshid S., et al, Nature Protocols 9, 1621 (2014); Ghatak A.S. et al, Crystal Growth & Design 16, 5323 (2016); Krishnan V. et al J. Advanced Pharmaceutical Technology & Research 4, 78 (2016); Govada, L. et al, Sci. Rep. 6, 1,(2016); Nanev, C.N., et al, Scientific Reports, 7, 35821 (2017); Pechkova E., et al, Nature Protocols 12, 2570 (2017); Nanev C., et al, IUCrJ 8, 270 (2021).[2] Hašek, J. Zeitschrift fur Kristallogr. 23, 613 (2006); Hašek, J. J. Synchrotron Radiation 18, 50 (2011)

Supported by projects MEYS ERDF fund (CZ02.1.01/0.0/0.0/16_013/0001776) and the Czech Academy of Sciences no. 86652036.

Protein crystallization is an ideal theoretical model for studying nucleation and growth of crystals due to features like slow kinetics. In the research field of crystal nucleation, there are a number of important theories describing the nucleation process. Among the theoreis, nucleation from dense liquid droplets after a process called liquid-liquid phase separation (LLPS) is widely accepted. According to this theory, the number and distribution of the phase separated droplets can determine the number, size and distribution of the final crystals in the solution. Here in this report, we will present our effort to obtain a single, suspended crystal in the crystallization solution through manipulation of the phase separated droplets. It is known that gradient magnetic field can exert magnetic force on the objects in the field so that gradient magnetic field can be fully utilized in protein crystallization [1-3]. By using a large gradient magnetic field we can merge the phase separated droplets in the solution non-contactly. The merged dense liquid droplet will be the location of protein crystallization and a single suspended crystal can be thus obtained. Figure 1 shows an example of suspened lysozyme crystal grown in a superconducting magnet. The results show that crystallization can be controlled via manipulation of the phase-separated droplets. Further, this study can also provide a strong support for the two-step nucleation theory.

The protein crystal has a wide range of potential applications (catalytic transformation, cell imaging and drug delivery) due to its highly ordered morphology. The hemoglobin, as the earliest discovered protein that can be crystallization, is the most commonly used protein crystal due to its mature crystallization process, lower cost, extensive source and can be mass produced. The protein crystal are generally prepared by vapor diffusion crystallization which already realize the size-controllable protein crystal in millimeter level. However, the preparation of protein crystal with micro-nano scale remains a challenge, which limits the application in the field of material science. In this study, the hemoglobin crystals in micron scale were prepared by stirring to make dense liquid phase well dispersive in the process of vapor diffusion crystallization, and successfully obtain the hemoglobin crystals around the size of 20 µm. Furthermore, nano-crystals were obtained by the water-in-oil micro-emulsion method. This work will boost the application of hemoglobin crystals in functional materials. Our next research will focus on the water-in-oil micro-emulsion process’ optimization to realize size-controllable and fine reproducibility.

The applications and potential advantages of serial crystallography, at both synchrotron and XFEL light sources, are growing. Despite advances in delivery methods, the sample volumes of micro-crystals required for serial crystallography, particularly time-resolved experiments, are still demanding. Batch crystallisation methods are the primary means in crystallographer's toolbox to create these samples. However, the process to convert single crystals grown by vapour diffusion to large volumes (> 100 µL) of micro-crystalline slurry can be exceptionally challenging. Here we present a strategy to perform this translation and it is divided into three stages: (1) optimising crystal morphology, (2) transitioning to batch, and (3) scaling. Given the variation of protein crystallisation, we hope that this protocol can act as a useful framework when attempting the conversion from vapour diffusion to batch. Tips and tricks will also be presented that may also be useful. Ultimately, we hope that this methodology improves the samples used for serial crystallographic studies and that this also improves the quality of acquired data.

Phosphine ligands are considered by many as one of the most significant class of ligands in organometallic chemistry. The search of new phosphine chelators, as well as the subsequent functionalization thereof, is a continuing process in order to induce appropriate properties for highly effective catalyst and to a lesser extend in medicinal purposes. Of particular interest is the search for water-soluble and highly stable ligands that can preserve their aquatic solubility even after metal coordination.

In this study, we aim to improve the efficiency of middle/late transition metal homogeneous catalysts (i.e. Re, Rh, Pd and Pt) and fac-[M(CO)₃] (M = Re and Tc) radiopharmaceutical synthons by selectively introducing monodentate and bidentate phosphine ligands consisting of various electronic and steric properties. The use of systematically altered bidentate phosphine ligands such as diphosphinoamine ligands has already been reported to show high selectivity improvements in catalytic reactions such as ethylene tri- and tetramerization [1].

A series of diphosphinoamine ligands was synthesized using methods described in literature [2, 3]. These ligands were then coordinated to various metal (i.e. Re(I), Tc(I), Pt(II) and Pd(II)). Results obtained from the biological analysis and catalytic evaluations have opened up a new window of opportunities for such compounds.

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Drugs in a crystalline state are preferably used due to their physicochemical stability [1]. Around 70% of the drug candidates to be newly available drugs have low solubility, which can compromise bioavailability and, consequently, product development [2]. Therefore, amorphous phases have become more attractive to the industry field as a promising strategy to improve solubility. The amorphous structure can be defined as a long-range tridimensional molecular packing loss. Compared to its crystalline counterpart, the amorphous can have higher inner energy that can increase the drug solubility, dissolution rate, and extension, improving the final formulation bioavailability. Several processes can be used to reach the drug’s amorphous structure, such as solvent evaporation, melting-cooling, lyophilization, and ball-milling. However, the amorphous drug metastability can induce structure recrystallization, which can be a problem [3]. Furthermore, different amorphization processes can promote local molecular packing variations yielding changes in the properties.

Herein, we combined the pair distribution function (PDF) and Reverse Monte Carlo (RMC) methods with data from a high-resolution diffractometer (model STADI-P, STOE^®) equipped with a MoKa₁ source, available at the “Laboratory of Crystallography and Structural Characterization of Materials” (LCCEM) at the Federal University of ABC, Santo André-SP, Brazil to analyze crystalline drugs under amorphization process. By the results, we could identify the amorphization mechanisms when using ball-mill and solvent evaporation process for different drugs, which can be induced by displacing O-O and O-H correlations (molecule distortions) as well as variations in hydrogen bonds. In both cases, the molecule was preserved after the amorphization process.

[1] D.A. Snider, W. Addicks, W. Owens, Polymorphism in generic drug product development. (2004). Adv. Drug Deliv. Rev. 56 391–395.

[2] B.Y. Shekunov, P. York, Crystallization processes in pharmaceutical technology and drug delivery design. (2000). J. Cryst. Growth. 211, 122–136.

[3] S.L. Raghavan, A. Trividic, A.F. Davis, J. Hadgraft, Crystallization of hydrocortisone acetate: influence of polymers. (2001). Int. J. Pharm. 212, 213–221.

The authors thank the financial support of The São Paulo Research Foundation (FAPESP) grant #2018/11990-5 and the National Council for Scientific and Technological Development (CNPq) grant #305661/2019-9.

Catalysis plays a vital role in numerous stages of petroleum refinement and fuel production, with one of the major energy sources globally being crude oil for fuels and further production of a variety of chemicals [1]. However, development of highly selective catalysts still poses a significant challenge in many of these processes [2]. Methanol carbonylation is one of the major homogeneously catalysed process for production of the acetic acid from methanol. With the oxidative addition of methyl iodide being the rate determining step in this catalytic process; the selectivity of the catalyst to favour the formation of the desired product may be achieved by carefully varying the ligand system of said catalyst as well as the reaction conditions[3]. The selectivity for acetic acid production with rhodium-based catalysts in a homogeneous medium is roughly 99% [4]. Catalytic rhodium system’s activity and selectivity are vastly improved by phosphine ligands leading to favourable results under milder conditions [5]. Our functionalised halogenated rhodium(I) complexes, [Rh(N,O)(CO)(PR₃)](R= Ph, Cy), coordinated to N,O bidentate Schiff-base ligands and select phosphine ligands are hereby reported. The extensive structural characterization of the complexes followed by the kinetic mechanistic study using UV/Vis, infrared and nuclear magnetic resonance spectroscopy will also be reported. The influence of halogens (F, Cl, Br) on the para-position of the Schiff base ligand on the methyl iodide oxidative addition to the rhodium(I) monocarbonyl specie will also be described .

[1] Lemonidou, A. A., Lappas, A. A. & Vasalos, L. A., 2011. Catalysis and Refinery. Thessaloniki: Encyclopedia of Life Support Systems

[2] Kumar, M, Chaudhari, R.V; Subramaniam, B; Jackson, T.A. Organometallics., 2014, 33, 4183−4191.

[3] Van Leeuwen P.W.N.M; Homogeneous Catalysis: Understanding the Art, 2004, Dordrecht: Kluwer Academic Publishers.

[4] Schurell, M., 1977. Rhodium catalysts for methanol carbonylation. Platinum Metals Reviews, 21(3), pp. 92-96.

[5] Osborn, J.A; Wilkinson, G; Young, J.F. Chem. Commun., 1965, 17.

The development of sterically encumbered ligands that contain anionic nitrogen donor sites (NR^2-) has played a pivotal role in advancing our overall knowledge of fundamental chemical reactivity throughout the Periodic Table. Recently, we are introducing a methyl-pyridine side arm in the β-diketiminato framework leads to a ligand that is tridentate in its nacnac imino-pyridine state (2,6-iPr₂-C₆H₃NC(Me)CHC(Me)NH(CH₂py))¹. Such ligands have not been used for compounds with low valent p-block elements. We presumed that additional donation from the nitrogen atom of the pyridine moiety may provide sufficient electronic stabilization that would compensate for the decrease in the sterics. Here we have successfully synthesized and characterized methylpyridinato β-diketiminate ligand stabilized chlorogermylene 1 which undergoes unusual smooth ring contraction in presence of Lewis acid (GeCl₂.dioxane) via C–N bond cleavage (2), facile dehydrocoupling and six membered Al-heterocycle formation (5), which are not observed for the nacnac based systems (Scheme 1). But, in presence of another Lewis acid containing group 13 element like AlCl₃, leads to the formation of dicholoaluminim complex 4 via the transmetallation process (Scheme 1). Single crystal X-ray study reveals that the pyridine moiety coordinates to the aluminum center in 4, possibly due to the radius of the aluminum atom is apparently too small compared to the ligand's bite angle, which leads to the asymmetric coordination. The work is another testimony to the fact that small variations can yield unprecedented outcomes.²

There is a wealth of materials that are beam sensitive and many of them only exist in nanometric crystals, because the growth of bigger crystals is either impossible or so complicated that it is not reasonable to spend enough time and resources to grow big crystals before knowing their potential for research or applications. This difficulty is encountered in minerals, zeolites, metal-organic frameworks or molecular crystals, including pharmaceuticals and biological crystals.

In order to study these crystals and potentially discover highly interesting materials a structure determination method that can deal with beam sensitive crystals of nanometric size is needed. The nanometric size makes them destined for electron diffraction, since electrons interact much more strongly with matter than X-rays or neutrons. In addition, for the same amount of beam damage, electron diffraction yields more information than X-rays [1].

The recently developed low-dose electron diffraction tomography (LD-EDT) [2] not only combines the advantages inherent in electron diffraction, but is also optimized for minimizing the electron dose used for the data collection. While using only minimal dose, the data quality is still high, allowing not only the solution of complex unknown structures, but also their refinement taking into account dynamical diffraction effects.

In this contribution we present several examples of crystals solved and refined by this method. The range of the crystals presented includes a synthetic oxide (Sr₅CuGe₉O₂₄), a natural mineral (bulachite) and a metal organic framework (Mn-formiate). The dynamical refinement can be successfully performed on data sets that needed less than 0.1 e^-/Ų for the entire data set.

[1] R. Henderson, Quarterly Reviews of Biophysics 28, 2 (1995), 171-193

[2] S. Kodjikian and H. Klein, Ultramicroscopy, 2019, 200, 12-19

Electron diffraction experiments and electron crystallography are experiencing a major leap in the nanocrystallography revolution [1]. Moreover, the use of the continuous rotation method (as in X-ray crystallography) for the collection of electron diffraction data is surpassing all previous data collection methods available in the past decade [2].

Unfortunately, there is no dedicated device for performing such experiments. All experiments found in the literature are done in (modified)-Transmission Electron Microscopes, as these are the only sources of electron beams. Though these devices are not optimal for performing such kind of experiments. Many factors play an important role here. In fact, scientist interested in using this technique, have even suggested on guidelines to use a (S)TEM as an electron diffractometer [3].

Therefore, there is a huge necessity that fully integrated electron diffractometers are available for the scientific community and industrial facilities. This necessity is now a reality. Here we present a novel device optimized and dedicated for electron diffraction experiments that uses the continuous rotation method. We will showcase this device and its advantages against electron microscopes that can perform ED measurements. We will show experimental evidence on the improvement of the data quality compared to data sets collected elsewhere. We will highlight the ease of use of this device.

The study of the structure of single crystals has typically been achieved with X-ray diffraction while many decades of progress and research have led to hardware improvements which have pushed the limits of X-ray diffraction. The current generation of home lab instruments allow the study of crystals down to about 1 micron in size with sources such as the FR-X, a high-power rotating anode¹.

In the quest to study even smaller samples than this, microED has become increasingly popular in recent years². As electrons interact more strongly with a crystalline sample than X-rays do, the study of samples smaller than 1 micron becomes possible and, in fact, necessary. We would like to introduce our solution for microED, the Synergy ED, along with results we have obtained using it, and efforts we have made to improve the quality of results.

1. Matsumoto, T., Yamano, A., Sato, T. et al. "What is This?" A Structure Analysis Tool for Rapid and Automated Solution of Small Molecule Structures. J Chem Crystallogr (2020).
2. Nannenga, B.L., MicroED methodology and development. Struct Dyn. (2020) 7(1).
3. Gruene, T. et al Rapid Structure Determination of Microcrystalline Molecular Compounds Using Electron Diffraction Angew. Chem. Int. Ed. (2018) 57(50): 16313–16317

Electron Diffraction (ED) as such has been around since the early days of Electron Microscopy. However, only since Transmission Electron Microscopes (TEMs) are available with accelerating powers of 200 to 300 kV and 2D detectors have become fast enough, Electron Crystallography really took off.

So far, ED could only been done in modified TEMs, resulting in challenging experiments and limited datasets, yet, structures could be obtained from samples in the range of merely tens of nanometers, that were unsolvable with either conventional or even synchrotron X-ray radiation.

For some reason, no dedicated Electron Diffractometer has been available commercially so far. Data quality would greatly benefit from a setup that focuses on the diffraction capability over imaging and allowing for faster and more complete datasets through proper 3D electron diffraction (3D-ED).

We will present a possible Electron Diffractometer design for Electron Crystallography from the point-of-view of X-ray Crystallography and indicate improvements over present TEM-based as well as X-ray instruments.

The class of transition metal phosphates (TMPs) shows a wide range of chemical compositions, variations of valence states and respective crystal structures. Among TMPs, VO(P₂O₇) and LiFePO₄ are of special interest as the only commercially used heterogeneous catalyst for the selective oxidation of butane to maleic anhydride [1] and cathode material in rechargeable batteries [2]. Due to their structural features, TMPs are considered as proton exchange-membranes in fuel cells, working in the intermediate-temperature range [2, 3]. We report on the successful ab initio structure determination of two novel titanium pyrophosphates, NH₄Ti(III)P₂O₇ and Ti(IV)P₂O₇, from X-ray powder diffraction data. Both compounds were synthesized via a new molten salt synthesis route. The low symmetry space groups P2₁/c (NH₄TiP₂O₇) and P-1 (TiP₂O₇) complicate the structure determination, making the combination of spectroscopic, diffraction, and computation techniques mandatory. In NH₄TiP₂O₇, titanium ions (Ti³⁺) occupy the TiO₆ polyhedron, coordinated by five pyrophosphate groups, one as a bi-dentate ligand. This secondary coordination causes the formation of one-dimensional six-membered ring channels with a diameter d_max of 514(2) pm, stabilized by ammonium ions. Annealing NH₄TiP₂O₇ in inert atmospheres results in the formation of the new TiP₂O₇, showing a similar framework consisting of [P₂O₇]^4- units and TiO₆ octahedra as well as an empty one-dimensional channel (d_max = 628(1) pm). The structures can be related to the high-voltage pyrophosphate cathode material Li₂FeP₂O₇ also crystallizing in P2₁/c [4]. Li₂FeP₂O₇ consists of a three-dimensional arrangement of undulating [Fe₄P₈O₃₂]_∞ layers [4] building a channel system that is occupied by Li⁺ ions. The structural relation to Li₂FeP₂O₇ implies a good proton conductivity of NH₄Ti(III)P₂O₇ and Ti(IV)P₂O₇. Both newly synthesized phosphates, NH₄Ti(III)P₂O₇ and Ti(IV)P₂O₇, show a proton conductivity based on the Grotthus mechanism. The activation energy of the proton migration of NH₄Ti(III)P₂O₇ belongs to the lowest which has been reported for this class of materials and indicates its potential application as a proton electrolyte in the intermediate temperature range. In situ X-ray diffraction study of the transformation of NH₄TiP₂O₇ to TiP₂O₇ reveals a two-step mechanism, the decomposition of ammonium ions coupled with the oxidation of Ti³⁺ to Ti⁴⁺ and subsequent structural relaxation.

Since its discovery, MgB₂ is presented as a candidate to replace conventional superconductors in several applications such as SMES and Magnetic Resonators. This possibility is based on its critical temperature (T_c), its low cost, and the possibility of forming cables by the “Powder In Tube” (PIT) method. Considerable research has been carried out to optimize the material and the cable conformation [1]. It was determined that the superconducting properties can be improved by inducing changes in the microstructure, with different synthesis methods [2], and/or the crystalline structure, by doping [3]. In this work, two different samples were prepared and characterized to find convenient methods to improve the material and the cables superconducting properties without increasing the cost.

The Mg (B_1-xC_x) ₂ samples were prepared starting from Mg and C-doped nano-B powders, with and without the addition of nano-SiC. The compounds were mixed in an agate ball mill inside a glove box. Then, they were compacted into pellets and sintered in a tube furnace with a circulating controlled Argon atmosphere. The samples were heat treated at two temperatures, 700ºC and 900ºC, for different periods. The specimens were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) (Fig. 1), and SQUID magnetometry. XRD data were refined by the Rietveld method with FullProf [4] as can be seen in Fig. 2. Finally, 700ºC in-situ syntheses were performed on a nano-SiC doped sample at the P61A line in DESY, to study the reaction development.

With these techniques, we were able to determine the lattice parameters, the existing phase percentages, the grain sizes, the stress state, and the T_c. These data together allow for a better understanding of the synthesis parameters and the effect of doping on the phase formation as a way to improve the superconducting properties of the material.

[1] Buzea, C. Yamashita, T., (2001). Supercond. Sci. Technol., vol. 14, no. 11, p. R115, 2001.

[2] Silva, L. B. S. Da, Serquis, A., Hellstrom, E. E., & Rodrigues, D. (2020). Superconductor Science and Technology, 33(4), 45013.

[3] Serrano, G., Serquis, A., Dou, S. X., Soltanian, S., Civale, L., Maiorov, B., Holesinger, T. G., Balakirev, F., Jaime, M. (2008). J. Appl. Phys., vol. 103, no. 2, pp. 1–5, 2008.

[4] J. Rodriguez-Carvajal (1990). Abstracts of the Satellite Meeting on Powder Diffraction of the XV Congress of the IUCr, p. 127.

Ruddlesden-Popper manganites La_xSr_2-xMnO_4-δ recently gained interest as promising electrode materials for solid oxid fuels cells. For 0.25 ≤ x ≤ 0.6, their stability under reducing atmosphere –along with the preservation of their K₂NiF₄-type I4/mmm symmetry –has been demonstrated using in situ high-temperature neutron and X-ray powder diffraction. [1] However, abnormally large anisotropic displacement parameters and complex changes in cell parameters point to the presence of disorder, which might explain the material’s increased electrical conductivity in diluted hydrogen. Submicron sized crystals are sufficient for electron diffraction (ED) to obtain two-dimensional single-crystal diffraction patterns, which can be interpreted in a more straightforward way than powder data. Therefore, single-crystal ED might pick up features which were missed during X-ray and powder diffraction. Using a dedicated environmental holder in a transmission electron microscope, we performed several series of in situ ED experiments to track structure transformations of La_0.5Sr_1.5MnO₄ upon heating in a 5% H₂ /He atmosphere. As the current state-of-the-art in situ equipment only permits tilting of the holder along one axis, conventional in-zone patterns cannot be obtained, and 3D ED is the optimal method to acquire sufficient diffraction data for structure analysis. We also performed the same experiments on Sr₂MnO₄ as a reference, since this material is known to undergo a space group transformation to a monoclinic P2₁/c supercell when reduced to Sr₂MnO_3.55 [2]. For La_0.5Sr_1.5MnO₄ a coexistence of both the tetragonal Ruddlesden-Popper phase and a perovskite phase has been noted upon heating to 750°C in reducing atmosphere, which has not been reported before. However, apart from the diluted hydrogen, the electron beam might possess some reductive power too, and the high temperatures can lead to decomposition. Therefore, we systematically examined the influence of different external factors, repeating the experiment with i.a. varying beam exposures, while heating in vacuum and reducing ex situ in 5% H₂ /He.

[1] Sandoval, M., Pirovano C., Capoen, E., Jooris, R., Porcher, F., Roussel, P., Gauthier, G. (2017). Int. J. Hydrog. Energy. 42 (34), 21930-21943.[2] Broux, T., Bahout, M., Hernandez, O., Tonus, F., Paofai, S., Hansen, T., Greaves, C. (2013). Inorg.Chem. 52 (2), 1009-1017.

Keywords: TEM, in situ, 3DED, Ruddlesden-Popper manganite, LSMO

This work was supported by BOF 38689 - New method to acquire in situ information on crystal structures changed by chemical reactions.

Metallic nanoparticles have been shown to have a wide variety of applications from catalysis to plasmonics and medicinal drug delivery [1-3]. The onset of functional properties not seen in bulk can be attributed to and finely controlled by particle size, shape, homogeneity, and chemistry [4-6]. Given nanoparticles’ small size – typically sub-100 nm – their properties can be strongly influenced by crystallographic defects such as twinning, interfaces, and surfaces. As such, a fundamental study of the energetics of atomic mobility at the surface of a nanoparticle can provide an invaluable understanding of the relationship between crystal structure and functional properties. Moreover, surface energetics play a key role in controlling nanocrystal growth and shape. In this study, Au nanoparticles with different organic ligands, and therefore different surface stabilities, are investigated in real space using quantitative atomic resolution aberration corrected scanning transmission electron microscopy (STEM).

STEM imaging has become one of the leading methods of materials characterization, and aberration correction has made atomic resolution imaging widely available. Advanced imaging and image processing techniques have been developed to quantify specimen features including thickness projected along the path of the beam [7-12]. Such quantitative methods generally rely on high angle annular dark field (HAADF) STEM, whereby images are formed using electrons that have been scattered to high angle with a strong atomic number dependence (so-called Z contrast). While these techniques have been applied to great effect under specific controlled conditions, most of the beam-specimen interaction is discarded both from lower scattering angles and via the angular and azimuthal integration of HAADF detectors. Such information is rich with detail about specimen morphology and can be used to improve quantitative precision when paired with image simulation.

Recently, the development of fast, high-dynamic range, direct electron detectors has made it possible to record the scattering distribution (k_x, k_y) as a function of probe position (r_x, r_y), generally referred to as 4D-STEM [13-15]. Such detectors have noise levels well below that of single-electron strikes, making them ideal for quantitative imaging. By collecting the whole scattering distribution at each probe position rather than integrating over an annulus, images can be formed using specific regions of the diffraction pattern that are most strongly affected by variations in thickness. Additionally, several images can be formed from the same dataset using different scattering regimes to further constrain thickness measurements.

Here we report on advances in quantitative thickness determination using 4D-STEM paired with multislice simulations. A detailed comparison of the advantages and challenges of using 4D-STEM opposed to conventional HAADF-STEM will be covered. Furthermore, we apply these 4D-STEM atom counting techniques to metallic nanoparticle systems to probe the energetics of beam-induced surface atom motion. The implications of such surface energetics on nanoparticle properties will be discussed.

1. Dreaden,et al. (2012). Chem. Soc. Rev. 41, 2740-2279.
2. Sau, et al. (2010). Adv. Mater. 22, 1805-1825.
3. Zhou, et al. (2011). Chem. Soc. Rev. 40, 4167-4185.
4. Balbuena, P. and Seminario, J. (2006). Nanomaterials: Design and Simulation, Elsevier: Amsterdam.
5. Yin, Y. and Alivisatos, A.P. (2005). Nature 437, 664-670.
6. Henry (2005). Prog. Surf. Sci. 80, 92-116.
7. LeBeau, et al. (2010). Nano Lett. 10, 4405-4408.
8. Van Aert, et al. (2013). Phys. Rev. B 87, 064107.
9. De Backer, et al. (2013). Ultramicroscopy 134, 23-33.
10. Katz-Boon, et al. (2013). Ultramicroscopy 124, 61-70.
11. Katz-Boon, et al. (2011). Nano Lett. 11, 273-278.
12. Dwyer, et al. (2012). Appl. Phys. Lett. 100, 191915.
13. Tate, et al. (2016). Microsc. Microanal. 22, 237-249.
14. Ballabriga, et al. (2011). Nucl. Instrum. Methods Phys. Res. 633, S15-S18.
15. Johnson, et al. (2018). Microsc. Microanal. 24, 166-167.

The authors acknowledge the use of the instruments and scientific and technical assistance at the Monash Centre for Electron Microscopy, a Node of Microscopy Australia. This research used equipment funded by Australian Research Council grant LE0454166.

Over the past few years, macromolecular structures have been successfully solved from Electron diffraction(ED) patterns using standard macromolecular X-ray crystallographic(MX) techniques[1]. This resulted in the emergence of a new field known as microED. MicroED is a very appealing technique as it allows for solving structures from nanocrystals thanks to the very strong electron-atom interaction. This is of great interest especially in protein crystallography where growing good quality macromolecular crystals up to micrometer sizes is often a challenge.
Besides, ED patterns provide information about the electrostatic potential which is a complementary information to the electron density maps provided by X-ray diffraction patterns. This can allow for example to determine accurately the location of positively charged ions. Although it is still necessary to grow nanocrystals with microED, as opposed to the popular cryo-EM imaging technique, there are evidence that microED should provide higher resolution than cryoEM[2]. On paper, the resolution with microED is in principle sufficient to resolve hydrogen atom positions.
Although microED has proven successful on an number of occurrences, theoretical works[3] suggest that dynamical diffraction corrupt the kinematic reflection intensities to the extent that solving macromolecular structures from standard MX techniques should not be possible for crystals larger than a few nanometres thick. In practice typical nanocrystals are a at least a few tens of nanometres which is an order of magnitude above the kinematic regime. This fact is partly reflected in the large R factors commonly found in microED which is usually in the 15-20% range. However, theoretical predictions usually offer much more pessimistic figures[4]. Moreover, even when Rfactor is improved using dynamical refinement technique, ED still fail to compete with R factors produced by X-ray techniques. As a result, there is still a great motivation in studying the effect of dynamical diffraction in electron diffraction experiments.
In this work, simulations of ED patterns have been performed on organic crystals with both the multislice algorithm(MS)[5,6] and the blochwave approach[6]. The differences between the 2 methods are presented with their advantages and modelling limitations.
Comparison with experimental patterns are presented for glycine and IRELOH with a discussion about differences between theory and experiment.
[1] Nannenga, B. L., & Gonen, T. (2019). The cryo-EM method microcrystal electron diffraction (MicroED). Nature Methods, 16(May), 369–379. https://doi.org/10.1038/s41592-019-0395-x
[2] Latychevskaia, T., & Abrahams, J. P. (2019). Inelastic scattering and solvent scattering reduce dynamical diffraction in biological crystals. Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials, 75, 523–531. https://doi.org/10.1107/S2052520619009661
[3] Glaeser, R. M., & Downing, K. H. (1993). High-resolution electron crystallography of protein molecules Robert. Ultramicroscopy, 52, 478–486.
[4] Oleynikov, P., Hovmöller, S., & Zou, X. D. (2007). Precession electron diffraction: Observed and calculated intensities. Ultramicroscopy, 107(6–7), 523–533. https://doi.org/10.1016/j.ultramic.2006.04.032
[5] Cowley, J. M., & Moodie, A. F. (1957). The scattering of electrons by atoms and crystals. I. A new theoretical approach. Acta Crystallographica, 10(10), 609–619. https://doi.org/10.1107/s0365110x57002194
[6] Kirkland, E. J. (2019). Advanced Computing in Electron Microscopy (Third Edit). Springer.
[7] Bethe, H. (1928). Theorie der Beugung von Elektronen an Kristallen. Annalen Der Physik, 392(17), 55–129. https://doi.org/10.1002/andp.19283921704

A well-known bottleneck in the structural characterization of macromolecules with X-ray diffraction is crystallization. Often the needed crystal size cannot be achieved despite extensive optimization of crystallization conditions. Nevertheless, the yield of sea urchin like needle clusters, microcrystals and almost two-dimensional platelets is a silver lining. Those crystals – too small for X-ray crystallography – could be applied to microcrystal electron diffraction (MicroED) methods.

3D electron diffraction (ED) is an uprising method for the structural characterization of nanocrystalline materials. ED has recently been applied to beam-sensitive materials like macromolecular crystals. Although there are also drawbacks for this method in protein crystallography, we used the spirit of the nanocrystallography revolution and started with first experiments on our transmission electron microscope.

So far we were able to acquire knowledge for the basic workflow for data collection with our instrument setup, a Zeiss Libra 120 plus TEM with an OMEGA energy filter and a TVIPS TemCam-XF416(ES) detector. We collected continuous rotation electron diffraction data for the zeolite ZSM-5 and protein nanocrystals (lysozyme) under cryo conditions.

With these fundamental achievements we are on track to apply MicroED to more challenging crystals and also solve novel protein structures in the future.

The theory of electron scattering by crystalline materials is well-established,with two main approaches to the calculation of diffracted intensities: the Bloch-wave (or scattering matrix) method, and the Multislice method [1, 2].Both have been implemented in numerous simulation programs and compute the required large-angle convergent beam electron diffraction (LACBED )patterns. While the accuracy of these simulations can be very high [3] they are also computationally intensive and relatively slow even with modern high-performance computing facilities and graphical processing units(GPUs). In Bloch-wave simulations the limiting step is the inversion of acomplex, non-Hermitian matrix, while for multislice the use of many configurations in the frozen-phonon approximation can increase simulation timesby several orders of magnitude [1, 2]. As a result, simulation times aregenerally several minutes at best. Machine learning (ML) as a computational approach has been gaining prominence in recent years and the implementation of neural networksas universal approximators holds great promise for the solution of inverse and/or computationally difficult problems. Importantly, once trained, a ML calculation is fast – typically a few milliseconds on a GPU. In the caseof modelling electron scattering, this may allow an increase in speed of 5–6 orders of magnitude. Here, we explore the simulation of electron scattering using a variational autoencoder (VAE) [4]. The VAE takes as an input a 128×128 pixel image of the projected potential of a unit cell of cubic material in the [001] orientationand gives an output of the 000 LACBED pattern of the same size. The VAE is trained end-to-end using 5527 Felix[5] Bloch-wave simulations of cubic materials taken from the inorganic crystal structure database (ICSD).[6] The simulations were split 85:10:5 into training, validation, and test sets. Similarity was quantified using a zero-mean normalised cross correlationloss function Z.[7] The position of features in reciprocal space was fixedby choosing an angular range that varied in inverse proportion with lattice parameter. Using 500 Bloch waves,each simulation typically required∼400 seconds to complete running on acluster of 160 cores.The VAE uses convolutional encoder and decoder sub-models, both 2 layers deep, to access a 12-dimensional latent space of encoded LACBED patterns. Calculations on an Nvidia GTX 1080Ti GPU are∼3.6×10⁵ times faster than a 160-core felix simulation. In this exploratory trial,only 5527 out of the 42879 cubic materials available on the ICSD were used for model training. Even with this very limited training data set, some VAE simulations approach the accuracy of felix, while others only produce a poor approximation. We estimate that training on > 12000 simulations would produce losses Z <5%, giving a similarity equivalent to that between felix and experiment.[8]

References

[1] B. G. Mendis,Electron beam-specimen interactions and simulation meth-ods in microscopy(John Wiley & Sons, 2018).

[2] E. J. Kirkland,Advanced computing in electron microscopy(Springer, 1998).

[3] L. J. Allen, S. Findlay,et al., Ultramicroscopy 151, 11 (2015)

[4] D. P. Kingma and M. Welling, in Auto-encoding variational bayes (International Conference on Learning Representations, 2014).

[5] R. Beanland, K. Evans, R. A. R ̈omer, and A. J. M. Hubert, Felix Bloch wave simulation: Source code, 2021.

[6] A. Belsky, M. Hellenbrandt, V. Karen, and P. Luksch, V. 58. N. 3.58,364 (2002).

[7] R. Beanland, K. Smith, P. Vanˇek, H. Zhang, A. Hubert, K. Evans, R. A.R ̈omer, and S. Kamba, Acta Crystallographica Section A77, (2021).

[8] A. J. M. Hubert, R. Romer, and R. Beanland, Ultramicroscopy 198, 1(2019)

The most conclusive and elucidating component of any small or macromolecular study is the proper structure determination. The two most commonly used tool for structure determination are being nuclear magnetic resonance spectroscopy (NMR) and X-ray diffraction. While both these techniques are extremely popular but have certain limitations. Recently a new technique 3D Electron Diffraction (3D ED) data collection for getting near to atomic resolution structures has taken a leap in last few years. In this method, once the intensities are extracted, the structures are obtained from the 3D ED data using similar tools as for X-ray diffraction structure determination like SHELX, olex2, etc. In general Independent atom model (IAM) is used for solving the structures, where a precomputed model of electrostatic potential is built using scattering factors from isolated, spherically averaged atoms or ions.¹ In reality the atoms in a molecule are not isolated and spherical, moreover, the usage of improper electron scattering factors in refinement may lead to physically unrealistic values. To overcome this, an aspherical TAAM refinement has been applied both for X-ray and ED refinement which largely improved the physical representation and refinement statistics of the structure.² We have chosen a model molecule β-glycine for this study for which 3D ED data is already available.³ Spherical and Aspherical TAAM refinement seemed to be possible in MoPro with the inclusion of electron scattering factors. Aspherical electron scattering TAAM model will be constructed using ELMAM2 and MATTS databank and refinement will be performed using MoPro. A comparison will be shown between reported data and spherical and aspherical TAAM refinement using MoPro and various statistics will be presented.

The material system YMn₂O₅ has several low temperatures phases, where magnetism and ferroelectricity occur. Especially, the origin of the ferroelectricity (FE) in a phase below T_FE = 39 K is an open question. The Literature agrees upon a magnetically driven principal mechanism from changes in the Mn spin configuration, which may be based either on magnetostriction due to symmetric exchange, the antisymmetric inverse Dzyaloshinskii-Moriya interaction or a combination of the two. Both mechanisms are accompanied by specific atomic displacements of ions in the structure. The space group Pbam (55) of the paraelectric phase does not allow the respective polar displacements and a refinement of the charge structure in a lower symmetric phase has not been successful so far, as the applied conventional structure analysis methods lack the required spatial resolution for the expected positional deviations.

We apply the new Resonantly Suppressed Diffraction (RSD)³ method, which is sensitive to minuscule structural changes in the sub-pm range, to shed new light on this controversial discussion. RSD is a structural characterization method in the field of Resonant Elastic X-ray Scattering and tunes the photon energy such that certain reflections approach zero due to destructive interference.

Here, we employ RSD on carefully chosen Bragg reflections below and above T_fE. With the data above T_FE we refined the static and dynamic displacements of the paraelectric phase, to receive an improved starting model for the structural characterization of the FE phase. With this starting model we were able to characterize the FE phase and consolidating the findings about the origin of ferroelectricity in YMO.

³Richter, C., Zschornak, M., Novikov, D. V., Mehner, E., Nentwich, M., Hanzig, J., Gorfman,S. & Meyer, D. C. Nature Communications, 9, 178 (2018).

Breast cancer is the leading cause of cancer death in women worldwide. Systemic changes in the elemental composition of the microenvironment between the cancer cells and the host stroma play an important role in supporting the growth and progression of the tumor. Excessive accumulation of the trace elements Fe, Zn, and Cu and its relationship with the matrix of the tumor microenvironment remodeling has been reported. Although the knowledge of breast carcinogenesis is being progressively elucidated with 2D cell-culture experiments, they are not able to reproduce the real physiological pattern of the tumor microenvironment where the surroundings cells are equally as important as the tumor cell itself. X-ray fluorescence (XRF) has been successfully exploited to detected trace elements in breast tissues, nevertheless, this technique is not sensitive to light elements such as carbon and oxygen, the major constituents of the breast tissue matrix. This information can be complemented by using the Rayleigh-to-Compton ratio technique (R/C). Likewise, the microenvironment remodeling comprises collagen fibrils rearrangements which can be investigated by Small-angle X-ray scattering (SAXS). Therefore, it will be shown the results of a pilot experiment exploiting the complementarity of the X-ray scattering and spectroscopy signals tomographically acquired, to map three-dimensionally the changes due to cancer progression.

Refractory materials structural and surface changes by sulfuric acid treatment E. Nushi¹, L. Gjurgjaj², A. Mele^1,21Center of Techniques Studies, Ivodent Academy, Rr. “Prokop Myzeqari, nr.10, Tirana, Albania enida.nushi@ivodent.org altin.mele@ivodent.edu.al ²Department of Chemistry, Faculty of Natural Sciences, University of Tirana, Bulevardi “Zog I”, nr. 25/1, 1016-Tirana, Albania lorenci.gjurgjaj@fshnstudent.info

Prrenjas clay mineral is used as refractory material in the metal casting and is found in southeast of Albania. It has a high content on bentonite. The influence of the sulphuric acid activation on the composition, structure and surface properties of Prrenjas clay mineral is investigated in this study by means of elemental chemical analysis, X-Ray Diffractometry, IR Spectroscopy and gas adsorption-desorption measurement. H₂SO₄ concentrations of 0.143 M, 0.232 M, 0.371 M, 0.537 M, 0.734 M, 0.927 M and 1.456 M were used in the treatment of samples. The treatment by increasing the acid concentration brings the leaching of Al³⁺, Fe²⁺, Mg²⁺ from the clay structure. The specific surface area and the pore volume of the clay samples increases respectively from 83 m²/g and 0.069 cm³/g for the untreated clay to 420 m²/g and 0.384 cm³/g for the clay mineral treated with 1.456 M H₂SO₄ solution. New mesopores were created during the acid activation mainly in the range of 2 – 8 nm. For the samples treated with 0.927 M and 1.456 M solutions the increase in specific surface area and pore volume is very high. The cationic exchange capacity decreases steadily with the concentration of H₂SO₄ used for the treatment.

[1]Steudel, A., Batenburg, L. F., Fischer, H. R., Weidler, P. G., Emmerich, K. (2009). Appl. Clay Sci. 44, 105-115.[2] Komadel, P., Schmidt, D., Madejova, J., Cicel, B. (1990). Appl. Clay Sci. 5, 113-122.[3]Madejova, J., Budjak, J., Janek, M., Komadel, P. (1998) Spectrochim. Acta 54, 1397-1406.[4] Kahr, G., Madsen, F. T. (1995). Applied Clay Sci., 9, Alexandre, 327-336.

Keywords: clay mineral; acid activation; surface properties

The present work is based on the development of a new lead-free perovskite system (Ba_1-xCa_x)(Sn_0.11Zr_0.05Ti_0.84)O₃ (BCSZTx); 0≤x≤0.20, exhibiting ferroelectricity in an average cubic structure [1]. The x-ray diffraction measurements have shown a simple cubic phase with Pm-3m space group for all the compositions. Despite having a centrosymmetric cubic phase, a slim hysteresis loop has been observed via PE loop measurements. Raman spectroscopic measurements have revealed the presence of local ordering in the macroscopically cubic matrix, corresponding to ‘A’ and ‘B’ sites. The cooperative behaviour of ‘A’ and ‘B’ site off-centered (local) atoms leading to microscopic polar symmetry in the macroscopically cubic matrix is held responsible for the observed ferroelectricity [2-4]. Owing to the aforementioned contrapositive behaviour, these ceramics have shown a diffuse dielectric phase transition with relaxor nature and thus exhibit a high value of dielectric constant. Eventually, we have clearly observed a decisive role of Ca²⁺ dopant at ‘A’ site in BCSZTx ceramic system leading to the enhancement in the ferroelectric and dielectric properties. The presence of a slim hysteresis loop along with broad and diffuse dielectric nature makes these ceramics a potential candidate for energy storage applications.

References:

[1] Y. Yao, C. Zhou, D. Lv, D. Wang, H. Wu, Y. Yang, and X. Ren, EPL (Europhysics Letters) 98, 27008 (2012).

[2] D. Fu, M. Itoh, S.-y. Koshihara, T. Kosugi, and S. Tsuneyuki, Physical review letters 100, 227601 (2008).

[3] A. K. Singh, D. N. Dubey, G. Singh, and S. Tripathi, EPL (Europhysics Letters) 130, 36002 (2020).

[4] V. Buscaglia, S. Tripathi, V. Petkov, M. Dapiaggi, M. Deluca, A. Gajovic, and Y. Ren, Journal of Physics: Condensed Matter 26, 065901 (2014).

The (E)-N-benzylidene-4-haloanilines belong to the Schiff base family, an important class of organic compounds which appears as an intermediate in several biological processes and during synthesis of organic compounds, due to the presence of azomethine group it finds extensive applications in analytical, coordination chemistry and biochemistry[1]. Some patents included versatile applications of this type of compounds, for example, in the protection of the skin against the harmful effects caused by sun exposure (Erythema), as well as the importance of mixtures of N-benzylideneanilines with aqueous acid solutions used as anticorrosives[2].The use of organic solvents translates into a significant environmental cost, which is why synthetic methods have been developed that do not involve solvents and involve other principles of green chemistry; the clean and efficient preparation of imines in aqueous suspension is one of them, in which acid catalysis is not necessary and provides relatively high yields when 1: 1 mixtures of aromatic aldehydes are reacted with primary aromatic amines[3]

In the X-ray powder diffraction crystallography literature, there are still no records for the resolution of the structure of the (E)-N-benzylidene-4-fluor(chloride)aniline, although for the other two haloanilines there are available data obtained in a previous work made by a former undergraduate student. The resolution of the structures was made using a D8 ADVANCE with DaVinci geometry, these data, as well as the other different spectroscopic results will be exposed and discussed in the poster.

In this work, the results obtained by single X-ray diffraction (XRD); even if for larger R-factor, are confirmed by another independent technique, one can study the vibrational spectroscopy with symmetry and group theory character tables. This method can be applied on the whole molecule or a part of it, mainly we search for function groups such as H₂O, an ionic part such as NH⁴⁺ or metal halide such as (MnBr_x). The fine XRD data results five possible solutions for the same molecule with the same chemical formula, although the R-factor values are so close, this method can distinguish between these possible solutions upon the crystal structure. The study of C₅H₁₀(NH₃)₂(MnCl₄Br₂) results one solution of XRD is confirmed by IR and Raman spectroscopy.

The space group of the molecule Ima2 with R= 3.33, The (MnCl₄Br₂) belongs to D_4h of 5 Raman peaks and different 5 IR peaks.

The Mn₂(MnCl₄Br₂) is C₂, C_2h or C_s according To the location of Mn atoms to the octahedral, the suitable solution is C_2h which expects 12 IR and another 9 Raman peaks with good agreement with IR and Raman results.

References

1. J. R. Ferraro, "Low-Frequency Vibrations of Inorganic and Coordination Compounds", Plenum Press, New York (1971).
2. M. S. Dresselhaus G. Dresselhaus and A. Jorio. Group theory: Application to the physics of condensed matter (Springer, Berlin, Germany, 2008) CH8.
3. G. Herzberg. Molecular spectra & molecular structure: II Infrared & Raman spectra of polyatomic molecules (Von Nostrand Reinhold comp., New York, USA, 1945) pp. 462-487.
4. K. Kamaras, L. Badeeb, M. Özeren, A. Pekker, S. Abdel-Aal, A. S. Abdel-Rahman, P. Andricevic, L. Forro and E. Horvath, Bulletin of the American Physical Society, MARV20013K (2019).
5. S. K. Abdel-Aal, A. S. Abdel-Rahman, W. M. Gamal, M. Abdel-Kader, H. S. Ayoub, A. F. El-Sherif, M. Fawzy, S. Bozhko, E. E. Yakimov and E. B. Yakimov, Acta Crystallographica B75(5) 880-886 (2019).

Single molecule magnets (SMM) are an interesting topic within the domain of materials chemistry, with possible uses for quantum computing and high density data storage. This study is concerned with the use of polarized neutron diffraction (PND) to describe

them.

If a SMM crystal sample is measured with a classical magnetometer, it would yield a simple vector sum of all site magnetizations in the crystal. To access the anisotropic magnetic susceptibility tensor of the individual sites, (PND) can be used. Neutrons will scatter as a result of both the magnetic and the nuclear strong force interaction. In a (PND) experiment we measure the combined diffraction pattern from both interactions, but want to isolate the magnetic part in order to calculate the anisotropic susceptibility tensor. I.e. we need to find the contribution from nuclear strong force separately, which can be calculated from the crystal structure. The structure is usually found using unpolarized neutron diffraction, as opposed to XRD because of the importance of scattering from light elements. However neutron diffraction experiments are significantly harder to come by, this study has investigated the effect of using a high quality XRD structure as a basis instead.

Two known molecular magnets, have been investigated: One with a Co(II) and one with a Dy(III) ion core. For both systems, susceptibility tensors are refined using both a neutron diffraction structure and different X-ray diffraction structures. The X-ray results are compared to the neutron tensor to gauge the impact on the refinement. Ultimately the goal is to decide if X-ray diffraction could be considered as a substitute for neutron diffraction when solving the crystal structure

of a molecule with the aim of finding the magnetic susceptibility.

The magnetic materials group at Diamond Light Source contains 4 world leading instruments for the study of different aspects of magnetic and strongly correlated materials.

• I06 - The Nanoscience beamline exploits the brightest region in Diamond’s spectrum, providing a high photon flux density for soft X-ray experiments. It combines microfocused soft X-rays with variable linear and circular polarisation and X-ray photoelectron emission microscopy (PEEM) to provide spectroscopic data on nanometre length scales. The intense polarised beam can be focused to a spot several microns in diameter, allowing the PEEM to probe nanomagnetism and nanostructures.
• I10 - Beamline for Advanced Dichroism Experiments (BLADE). BLADE delivers soft X-ray beam in the energy range from 0.4 to 2 keV. The research focuses on the magnetisation and the magnetic structure of novel nanostructured systems. These magnetic properties can be probed thanks to high dichroic effects in the soft X-ray region. The dichroic effect can be studied both in absorption and scattering experiments.
• I16 - Hard x-ray materials and magnetism beamline. This beamline provides high flux in the tender-hard x-ray energy regime, from 2.7-15 keV, ideal for looking at resonant edges of most 3d, 4d and 5d metals. A large kappa-diffractometer allows diffraction in a range of geometries from several sample environments including a 4K cryostat and 1T magnet. Full polarisation control and analysis is available with a double-crystal phase retarder and linear polarisation analyser.
• I21 - This is a dedicated Resonant Inelastic soft X-ray Scattering (RIXS) beamline that provides a highly monochromatised, focused and tunable X-ray beam onto materials, while detecting and energy-analysing scattered X-rays using a spatially-resolved two-dimensional detector. By studying the energy and momentum differences between the incident and the outgoing X-rays, one can obtain information such as the local lattice structure (local crystal field), electron orbitals (orbital excitations), collective lattice vibration (phonons), magnetic (spinons/magnons) and charge excitations of the material under investigation.

For more information, please come to the poster or see https://www.diamond.ac.uk/Instruments/Magnetic-Materials.html

The next proposal deadline is: Wednesday 7th October 2020

https://www.diamond.ac.uk/Users/Apply-for-Beamtime.html

The pseudogap state in high transition temperature copper oxide superconductors shows many unusual magnetic, electrical phenomenon. A principal issue is to understand the origin of the pseudogap phase in the high transition temperature copper oxide superconductors¹. An important controversial problem is whether the pseudogap phase is a crossover from the superconducting phase or a distinct phase. If it is the latter, the symmetry changing which cause of magnetic/electric order will be observed by phase transition. There are several evidences from angle-resolved photoemission spectroscopy (ARPES)² and polarized neutron diffraction³ show that the time-reversal symmetry is broken at the pseudogap phase. However, X-ray optical activity (XOA)⁴ showed not time-reversal symmetry but mirror symmetry broken.

Here we report the persuasive evidence of spatial-inverse symmetry and time-reversal symmetry broken by using our original machine, the generalized-high accuracy universal polarimeter(G-HAUP)^5,6. G-HAUP enables us to measure the optical rotation (OR) and the circular dichroism (CD) in addition to the linear birefringence (LB) and the linear dichroism (LD), simultaneously. When the spatial inversion symmetry is broken, reciprocal OR and CD, i.e., optical activity (OA) and natural CD (NCD), can be observed. On the other hand, when the time reversal symmetry is broken, non-reciprocal OR and CD, i.e., Faraday rotation (FR) and Magnetic-CD (MCD), can be observed.

1. Norman, M. R., Pines, D. & Kallin, C. Adv. Phys. 54, 715–733 (2005).

2. A. Kaminski et al., Nature, 416, 610 (2002)

3. S. De Almeida-Didry et al., Phys. Rev. B, 86, 020504 (2012)

4. M. Kubota et al., J. Phys. Jap., 75, 053760 (2006)

5. J. Kobayashi, T. Asahi, M. Sakurai, M. Takahashi, K. Okubo, Y. Enomoto, Phys. Rev. B, 1996, 53, 11784-11795.

6. M. Tanaka, N. Nakamura, H. Koshima, T. Asahi, J. Phys. D: Appl. Phys., 2012, 45, 175303-175310

The competing or cooperative character between different degrees of freedom lead to different ground states in strongly-correlated systems. Even simple systems, such as pure rare earth compounds, present multiple phase transitions with complex magnetic structures in some of them, resulting from a strong interplay between magnetic dipolar interaction and temperature dependence of crystal field parameters [1]. So, it is expected that some rare-earth-based compounds also have rich magnetic phase diagrams. One example is the series of intermetallic compounds RNiSi₃ (R = rare earth), which shows anisotropic antiferromagnetic ground states evolving with R [2-4]. The microscopic magnetic structures must be determined to rationalize such rich behavior. Here, resonant X-ray magnetic diffraction experiments are performed on single crystals of GdNiSi₃, TbNiSi₃ and HoNiSi₃ at zero field. The primitive magnetic unit cell matches the chemical cell below the Néel temperatures T_N = 22.2, 33.2 K, for Gd- and Tb-based compounds, respectively. The magnetic structure is determined to be the same for both compounds (magnetic space group Cmmm′) and could be fully described by a single one-dimensional irreducible representation of the Cmmm space group. It features ferromagnetic ac planes that are stacked in an antiferromagnetic + − + − pattern, with the rare-earth magnetic moments pointing along the a direction [5]. For HoNiSi₃, the situation is more complicated, since this compound show two well-defined λ-shape anomalies at T_N1 = 6.3 K and T_N2 = 10.4 K. Additionally, different components of the total magnetic moment order at different temperatures. The a component orders at T_N2, and after further cooling above T_N1, the c component orders. For this compound, our results show that at temperatures between T_N1 and T_N2 (phase II), the ordered magnetic moment points along the a-axis, while below T_N1 (phase I), the ordered magnetic moments have components both along with a and c. Remarkably, while at phase II the possible magnetic structure is the same as found in GdNiSi₃ and TbNiSi₃, at phase I two irreducible representations are needed to account the total magnetic moment direction. In this phase, the magnetic structure is consistent with C2’/m magnetic structure. Lastly, those magnetic structures contrasts with the + − − + stacking and moment direction along the b axis previously reported for YbNiSi₃ [6]. This indicates a sign reversal of the coupling constant between second-neighbor R planes as R is varied from Gd, Tb and Ho to Yb. The long b lattice parameter of GdNiSi₃ and TbNiSi₃ shows a magnetoelastic expansion upon cooling below T_N, pointing to the conclusion that the + − + − stacking is stabilized under lattice expansion. A competition between distinct magnetic stacking patterns with similar exchange energies tuned by the size of R sets the stage for the magnetic ground state instability observed along this series.

Rare earth rich intermetallic compounds of the type R₃T (R = rare earth, T = transition metal) are found to be formed by very limited elements because of negative heat of formation and these compounds are revisited several times due to various novel properties emerging out of their crystal and magnetic structures. [1] Tb₃Co is one such compound which orders below T_N = 84 K (Fig. 1) and goes through a first order magnetic transition of order to order type at ~72 K. Despite of several previous studies on this compound the reason behind the low temperature transition like feature was remain unexplained. It was revealed by our temperature dependent neutron diffraction study (Fig. 2) that the magnetic structure of this compound remains unaltered below 72 K to the lowest temperature except for some changes in intensity and moment values. The Rietveld refinement analysis to these data suggests that there is a drastic change in lattice parameters and volume around 40 K clearly suggesting a presence of strong spin-lattice coupling in this compound. Further, magnetic field dependent neutron diffraction data and the refinement analysis performed over the high angle part of these field dependent patterns confirms that there exists a change in strength of the spin-lattice coupling which is stronger at lower temperature and getting weaker at higher temperature. This is what responsible for the low temperature drop in ZFC in this compound. [2] Moreover, strong frequency dispersion in linear and nonlinear ac- susceptibility data and their various analyses confirm that Tb₃Co exhibits magnetic glassy behaviour with magnetic glass temperature coincides with first order transition temperature at 72 K. [2] Further, various time dependent dc- magnetization measurements provide evidences for the fact that the magnetic glassy behaviour persists in this compound even up to P ~ 1 GPa although the fitting to stretched exponential equation to the magnetic relaxation data infers that the glassy behaviour is weakened enough at P = 0.69 GPa and further increase in pressure has marginal effect on the glassy behaviour in this compound. [3] However, apart from shifting the transition temperatures to lower temperature (T_N by 6 K, First order transition by 15 K and low temperature transition like feature by 3 K) with increasing pressure up to 1.21 GPa, pressure is found to improve the magnetocaloric property of this compound (Fig. 3) to a large extent. The difference between -ΔS_M in presence of P ~ 1 GPa and at ambient condition is plotted in Fig. 3 and it is exhibiting a strong peak thereby inferring an enhancement of 37% in magnetocaloric effect in Tb₃Co at P ~ 1 GPa.

[1] Buschow, K. H. J. (1977) Rep. Prog. Phys 40, 1179.
[2] Goswami, S., Babu, P. D., Rawat, R. (2019). J. Phys. Condens. matter 31, 505802.
[3] Goswami, S., Babu, P. D., Rawat, R. (2019). J. Phys. Condens. matter 31, 505802.

One-dimensional spin chain systems have been attracting renewed interest in terms of a magnon/spinon-band splitting, which is found in ?-Cu₂V₂O₇ [1] and Cs₂CuCl₄ [2]. Nonreciprocal propagation of such quasiparticles is of growing interest since it may be used for spintronics device realization. A key parameter for the band splitting is an intrachain antisymmetric Dzyaloshinskii-Moriya interaction. To expand the variety of materials that can exhibit the band splitting, we have further searched for a possible quasi one-dimensional antiferromagnet. Cu₂(MoO₄)(SeO₃) is a candidate quasi one-dimensional compound, which crystallizes in a monoclinic system (space group P2₁/c) with the unit cell parameters ? = 104.675(12)˚, a = 8.148(5) Å, b = 9.023(5) Å, and c = 8.392(5) Å [3]. The Cu²⁺ ions are connected via edges of CuO₅, forming armchair-like chains along c-axis with three different bond lengths, 3.186 Å, 2.973 Å, and 3.149 Å. Due to the lack of local inversion symmetry between the shortest Cu(1)-O-Cu(2) bonds, the active DM interactions between these bonds could be expected.

We have performed single crystal magnetic susceptibility measurements and a neutron powder diffraction to characterize this compound. The magnetic susceptibility shows an anomaly at T_N ~ 23 K in all directions. The temperature dependence of the magnetic susceptibility shows a broad maximum near 50 K indicates a low-dimensionality and short-range correlation. The magnetic susceptibility was fit between 130 K < T < 300 K to the Curie-Weiss law and the Curie-Weiss temperature Θ = -68(1) K was obtained. The negative Curie-Weiss temperature confirms that the dominant exchange interaction between Cu²⁺ ions in Cu₂(MoO₄)(SeO₃) is antiferromagnetic. Moreover, the magnetic susceptibility strongly depends on the crystallographic direction suggesting that the g-factor in this compound is anisotropic. A sharp drop in the susceptibility only along c-axis is observed suggesting that the majority spins align along this direction.

A neutron powder diffraction experiment was carried out on HB2A powder diffractometer at High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory (ORNL). Ge(113) monochromator was used to select neutrons with λ = 2.41 Å. Magnetic Bragg reflections were observed below T_N on top of the structural reflections indicating the magnetic propagation vector q = (0 0 0). Magnetic structure analysis was performed using the representation analysis method; we found that Cu₂(MoO₄)(SeO₃) orders with antiferromagnetic structure, where the magnetic moments are mostly parallel (or antiparallel) to the chain direction.

[1] G. Gitgeatpong, et al., Phys. Rev. Lett. 119, 047201 (2017)

[2] K. Yu. Povarov et al., Phys. Rev. Lett. 107, 037204 (2011)

[3] S. Y. Zhang, H. et al, Inorg. Chem., 48 (24), 11809–11820 (2009)

Iron borate FeBO₃ (space group) is a known crystal which exhibits specific magnetic, magnetoacoustic, magnetooptical, and resonance properties [1,2]. It was proposed to use such crystals for monochromatization of synchrotron radiation in nuclear resonance spectroscopy as the so-called synchrotron Mössbauer source (SMS) [1,2]. The spectra of reflected radiation strongly depend on the hyperfine interactions in this crystal, while the required radiation parameters are achieved near the Néel point (T_N ~ 348,5 K) [1]. In this case, precise studies of the magnetic, electronic, and structural properties of an iron borate single crystal, especially near the Néel point, are of a great importance.

Studies were carried out by means of conventional Mössbauer spectroscopy and single crystal X-ray diffraction analysis. The iron borate single crystals were previously synthesized using the flux-growth technique [1,2]. High structural perfection of the studied FeBO₃ and⁵⁷FeBO₃ crystals was confirmed by X-ray measurements.

The Mössbauer spectra were processed in the framework of the combined magnetic and electric hyperfine interactions taking into account the nonresonant background and the effective thickness of the absorber. At T< T_N, the magnetic moments of two sublattices m₁ and m₂ lie in the basal plane of the crystal and are oriented at an angle of J ~ 179.17 [3]. It was found that the main axis of an electric field gradient (Z') is orthogonal to the moments m₁ and m₂ and does not change the orientation over the entire investigated temperature range 10-400 K (Fig.1).

The maximum entropy method was used to analyze the anisotropy of electron density distribution in FeBO₃. There is no evident of local disordering near the Fe sites below and above the the Néel point, (Fig. 2) which is consistent with Mössbauer data.

In addition, for the FeBO₃ single crystal, the hyperfine parameters were determined and the crystal structure was refined in a wide temperature range. The data obtained could be very useful for tuning pure nuclear diffraction in SMS experiments.

This study was funded by RFBR, project number 19-29-12016-mk.

[1] Smirnova, E.S., Snegirev, N.I., Lyubutin I.S. et al. (2020). Acta Cryst. B. 76, 1100.

[2] Yagupov, S., Strugatsky, M., Seleznyova, K. et al. (2018). . Cryst. Growth Des. 18, 7435.

[3] Pernet, M., Elmale, D. & Joubert, J.-C. (1970). Solid State Commun. 8, 1583–1587.

Members of the multiferroic RMn₂O₅ (R = Y, Bi and rare earth elements) family are well known for their concomitant presence of more than one order parameters at a given temperature [1]. Due to centrosymmetric structure of the mullite-type BiMn₂O₅ compound the microscopic origin of the multiferroicity was explained in terms of complex interplay between spin-ordering, highly polarizable Bi³⁺ with stereo-chemically active lone electron pair, Mn³⁺/Mn⁴⁺ charge-ordering and geometric distortions of the MnO_y coordination polyhedra. A cooperative antiferromagnetic (AFM) ordering between M³⁺ and Nd³⁺ was also observed for NdCrTiO₅ [2] and NdFeTiO₅ [3,4]. Below the respective T_N the M³⁺ cations become AFM and turn the Nd³⁺ cations into AFM along the ab plane through exchange coupling [2]. The collinearly ordered M³⁺ cations along the octahedral chain directing c-axis gives rise to magnetostriction, leading to multiferroicity in this compound [2]. In search of novel multiferroics, we report the synthesis and characterization of the mullite-type O10 phase isostructural NdMnTiO₅ compound. The crystal structural features are described using X-ray powder diffraction data Rietveld refinements. Complementary optical phonon analyses were carried out by infrared and Raman spectroscopy. The optical bandgap was obtained using both Tauc and recently introduced DASF [5-6] methods to determine type and energy of the transition, respectively. The enhancement of DC magnetic susceptibility is a common feature in rare-earth manganates. The Fisher’s heat capacity shows clear evidence of the onset of long range ordering. The large deviation between ZFC and FC susceptibility below the Néel temperature (43(1) K) indicates the presence of competing interactions and/or magnetic anisotropy in the orthorhombic system. Assuming weak interactions between Nd³⁺ and Mn³⁺ magnetic sublattices, the effective total magnetic moment was calculated from the temperature-dependent paramagnetic region, which lies close to theoretical spin-only magnetic moment values. The temperature-dependent magnetic susceptibility was modelled using the mean field approximation, where an interaction between the ordered Mn³⁺ spins and the electrons occupying the lowest lying Kramers' doublet of the Nd³⁺ cations was considered.

[1] A. Munoz, J.A. Alonso, M.T. Casais, M.J. Martinez-Lope, J.L. Martinez, M.T. Fernandez-Diaz (2002). Phys. Rev. B 65, 144423.

[2] J. Saha, G. Sharma, P. Patnaik (2014). J. Magn. Magn. Mater. 360,34.

[3] G. Buisson (1970). J. Phys. Chem. Solids 31, 1171.

[4] I. Yaeger (1978). J. Appl. Phys. 49, 1513.

[5] A. Kirsch, MM: Murshed, M.J. Kirkhame, A. Huq, J.F. Litterst, Th.M. Gesing (2018). J Phys. Chem. C. 122, 28280.

[6] A. Kirsch, MM: Murshed, J.F. Litterst, Th.M. Gesing (2019). J Phys. Chem. C. 123, 3161.

Keywords: Neutron; PXRD; multiferroic; crystal structure; Raman; magnetic property.

The conductive, magnetic, optical, and mechanical properties of the rare-earth RB₁₂ dodecaborides (R = Sc, Y, Tb, Dy, Ho, Er, Tm, Yb, Lu) are of significant interest both for basic research and for practical applications. The combination of metal conductivity with resistance to external influences makes them unique materials for use in extreme environmental conditions. In basic research, these compounds are conveniently used to study the properties caused by rare-earth metal ions.

The dodecaboride structure is formed by a strong framework of boron cuboctahedra (B₁₂). Metal atoms center the spacious B₂₄ cavities between the cuboctahedra and are loosely coupled to each other. The structure of rare-earth dodecaborides is most often described as cubic, sp. gr. Fm-3m. The problem complicating the characterization of the structure and properties of dodecaborides is that the B₁₂ cuboctahedra with the orbitally degenerate ground state are distorted by the cooperative Jahn-Teller effect, although to a very small extent.

The single-crystal structures of YbB₁₂, TmB₁₂, and LuB₁₂ were studied in the temperature range 88–293 K, and HoB₁₂ and ErB₁₂ - in the range 88–500 K using high-resolution X-ray diffraction data to correlate structural changes with changes in the physical properties of the studied dodecaborides. Lattice deformations caused by the cooperative Jan-Teller effect were detected. A method is used for approximating the temperature dependences of atomic displacement parameters (ADP) using the extended Debye or Einstein models [1]. The breakpoints of the temperature dependences of ADP found for HoB₁₂ ErB₁₂ and YbB₁₂, in combination with nonmonotonic changes in the lattice parameters near critical temperatures T_c, indicate phase transformations revealed by diffraction data. Lattice instability and rearrangement of the phonon spectrum near T_c are accompanied by the observed changes in physical characteristics.

The proposed method for modelling of temperature depending ADP is a sensitive structural diagnostics tool for detecting implicit phase transitions, quantum critical points, and quantum instabilities of various nature, leading to appearance of anomalies in the physical properties of crystals.

It was previously suggested that, under certain conditions, the formation of channels or stripes of conduction electrons in certain crystals could be associated with high-temperature superconductivity and colossal magnetoresistance. X-rays diffract from all types of electrons in the crystal, including conduction (delocalized) ones. The technical difficulty laying in the fact that conduction electrons have a low density and give a very weak diffraction signal was solved using special data collection and improved data processing techniques. The visualization of charge stripes in the studied dodecaborides using X-ray diffraction data was achieved by constructing difference Fourier syntheses of electron density without taking into account the crystal symmetry and by the complementary method of maximum entropy. Violations of the cubic symmetry of dodecaborides appeared in the orientation of the residual electron density in certain directions in the crystal. A correlation has been established between the anisotropic ED distribution and the anisotropy of conductivity [2].

The analysis of electron density distribution and the suggested visualization approach will provide the formation of systematic relationships between structure and physical properties and could be applicable to other crystals.

In pursuit of new materials in the topical area of low dimensional and frustrated magnetic systems we have begun to investigate a family of materials which use the oxalate ligand as a backbone from which multiple structures can be derived through combination with magnetic spin sources and additional ligand groups. We currently focus primarily on compounds which have first row transition metals as sources of magnetic spin [1][2], which can then be coupled in two-dimensional (2d) layered lattices.

Two such examples we have synthesised are the isostructural compounds CsM^II(C₂O₄)F (M= Co or Fe). These compounds comprise a layered 2d structure where magnetic exchange coupling is suppressed between layers by the presence of large Cs⁺ ions. Within the layers, the metal atoms are arranged in a rectangular lattice with the two coupling groups segregated in opposite axial directions (along the a axis – F^- coupling, along b axis – C₂O₄^2-, oxalate coupling). The strong two dimensionality plus the very clean in-plane rectangular coupling means this system in principle maps very nicely onto a 2d Heisenberg (3D) J₁/J₁’ type of model, which should be completely free of any diagonal (J₂) exchange coupling that might geometrically frustrate the system [3]. Theoretically this should either lead to an antiferromagnetic stripe order, or with sufficient inter-chain coupling to Néel long-range order (LRO) in the plane, with possible transitions between these states with temperature [3]. Additional coupling within the layers or between the layers may also lead to frustrated ground states, and there have been several theoretical and numerical studies of these kinds of idealised systems [4].

From elastic neutron powder diffraction data, while the two materials have a near identical nuclear structure, their magnetic superstructures are quite different when measured below their transition temperatures (100-150 K). In the Fe compound, the moments are aligned such that the antiferromagnetic coupling by the F^- and C₂O₄^2- groups dominates, creating a Néel state square lattice with ferromagnetic alignment between layers. The Co material while maintaining the F^- antiferromagnetic coupling, conversely displays ferromagnetic coupling across the C₂O₄^2- group. This leads to antiferromagnetic coupling across the Cs⁺ layer. This difference in magnetic structure is currently being investigated by examining system excitations to determine the energy differences between these two states but it is known that the oxalate ligand can support both types of coupling depending on its environment [5][6]. Examining this system more closely may give insight into the mechanisms and limits which govern how systems of this type order generally and so act as a basis for explaining more complex systems which may have frustrated character.

[1] W. Yao et al., Chem. Mater., 2017, 29, 6616.

[2] K. Sustain et al., Inorg. Chem., 2019, 58, 11971.

[3] P. Sindzingre, Phys. Rev. B, 2004, 69, 094418

[4] A. Orendacova et al, Crystals, 2019, 9, 6

[5] M. Peric et al, Monatsh Chem, 2012, 143, 569-577

[6] J. Vallejo et al, Dalton T., 2010, 39, 2350-2358

Thank you to ISIS Neutron and Muon Source and the University of St Andrews for their support of this work

The synthesis of coordination compounds based on 3d cations has been of great interest not only for their various structures and topologies but also for their possible applications as functional materials in areas such as gas storage/adsorption, catalysis, magnetism, luminescence, among others. [1-3]

Two new coordination polymers based on Co^II and Ni^II, {[Co(HL)(EtOH)₂](ClO₄)}_n(1), {[Ni(HL)(EtOH)₂](ClO₄)}_n(2) (H₂L = 2-{[(E)-1H-imidazol-4-ylmethylidene]amino}benzoic acid), were synthesized using a new Schiff base ligand. Compounds 1 and 2 are isostructural presenting a one-dimensional helical chain arrangement and crystallizing in a P21/n monoclinic space group. A hexacoordinated cation with an MN₂O₄ environment is present in the cationic fragment [M(HL)(EtOH)₂]⁺ being the charge balanced by a ClO₄^- anion. Furthermore, the carboxylate group of HL^- ligand is also acting as syn-anti bridge, producing the assembly of the [M(HL)(EtOH)₂]⁺ fragments, thus generating a cationic chain growing through the b axis with an intercation M∙∙∙M distance of 5.1257(13) Å and 5.164(4) Å for 1 and 2, respectively. The M-Ox distances are in the range of 2.060(3) Å to 2.136(4) Å for 1 and 1.988(3) to 2.107(4) Å for 2. Meanwhile, the M-Ny distances are 2.076(3) Å and 2.139(3) Å for 1 and 2.041(4) Å and 2.080(4) Å for 2. The resulting MN₂O₄ moiety presents an elongated octahedral geometry with higher bond distances in the axial position corresponding to the EtOH molecules. Magnetic susceptibility characterization in the 1.8–300 K range reveals intrachain antiferromagnetic interactions for 1 and ferromagnetic interaction for 2 with the presence of the zero-field splitting phenomenon in both compounds.

[1] F. J. Teixeira, L. S. Flores, L. B.L. Escobar, T.C. dos Santos, M. I. Yoshida, M.S. Reis, Stephen Hill, C. M. Ronconi, C. C. Corrêa, Inorg. Chim. Acta 511 (2020).

[2] Y. N. Belokon, V. I. Maleev, M. North, V. A. Larionov, T. F. Savel’yeva, A. Nijland, Y. V. Nelyubina://doi.org/10.1021./cs400409d.

[3] R. Jangir, M. Ansari, D. Kaleeswaran, G. Rajaraman, M. Palaniandavar, R. Murugavel, ACS Catal. 9 (2019) 10940-10950.

The authors acknowledge FONDECYT 1211394, Proyecto Anillo CONICYT ACT 1404 grant, CONICYT FONDEQUIP/PPMS/EQM130086-UNAB, Chilean-French International Associated Laboratory for Multifunctional Molecules and Materials-LIAM3-CNRS N°102 and CEDENNA, Financiamiento Basal, AFB180001.

Dense coordination polymers combine the functional properties typical of the traditional inorganic solid state, such as magnetism, with the remarkable tunability and flexibility that arises from the incorporation of molecular components. They therefore offer the opportunity to discover unusual behaviour that arises from the coupling of these properties. [1] Thiocyanate compounds have the potential for rich optical and magnetic properties, but both their chemistry and magnetism remain comparatively unexplored.

Metal framework compounds involving bridging thiocyanate ligands have started to establish themselves as a rewarding family of materials for magnetic studies, as the thiocyanate acts as an effective superexchange pathway between metal centres. [2] In addition, the asymmetric bonding requirements of the nitrogen and sulphur termini can often result in unconventional framework topologies. This, in turn, can lead to unusual magnetic structures and spin textures in the compounds.

Here will be presented three isomorphous metal thiocyanate frameworks, CsM(NCS)₃, where M = Ni, [3] Mn and Co; of which the latter two are new materials. The structures of these materials have been determined by single crystal X-ray diffraction to be post-perovskite two-dimensional frameworks with interplanar Cs counterions. Bulk magnetic susceptibility measurements revealed all the materials magnetically order between 6 and 16 K, with complex, non-collinear orderings. Following these results, neutron diffraction experiments of both single crystal and powder samples have been carried out to explore the unusual magnetic features further.

[1] W. Li, et al., Nat. Rev. Mater., 2017, 2, 16099.

[2] E. Bassey, et al., Inorg. Chem., 2020, 59, 11627 – 11639.

[3] M. Fleck, Acta Crystallogr. C60, i63 (2004).

Polynuclear coordination complexes with transition metal ions in intramolecular spin communications have been sought by both synthetic and theoretical chemists to step forward towards a new generation of magnets. In this context, manganese carboxylates are attractive systems owing to the variable oxidation states of the metal and the diversity of the carboxylate linker which impart unique characteristics to the frameworks. Manganese (II) compounds in the high spin ground state (S=5/2) are particularly important due to the possibility of the strong exchange interaction between the 3d-electrons. The magnetic centers with varying unpaired electrons provide a variety of magnetic ordering-spin frustrated multiferroics to single-molecule magnetism. Our group is adopting a crystal engineering approach to assemble high nuclear manganese clusters with varying coordination assemblies and explore the influence of selected aromatic dicarboxylic acids in different polar aprotic solvents on spin-exchange interactions. In this presentation, we discuss our strategy on the structural design of new manganese carboxylate coordination polymers and the influence of nonbonding interaction on overall assembly and its antiferromagnetic behavior.

As in the smaller doping range (0.0 ≤ x ≤ 0.5) [1,2], Nd_1-xSr_xFeO₃ adopts an orthorhombic (space group: Pnma) ABO₃ perovskite structure at room temperature, for all compositions within 0.1 ≤ x ≤ 0.9.

Magnetization measurements from 5K to 700K show weak antiferromagnetic behaviour and paramagnetism following the typical Curie-Weiss law above 600K. Assuming that the spin state of the Fe site is (LS Fe³⁺_y IS Fe³⁺_1-y)_1-x LS Fe⁴⁺_x, the ratio of intermediate spin (IS) Fe³⁺ gradually decreases as x increases, and it decreases rapidly when x≧0.6. This decrease in the ratio of IS Fe³⁺ with the increase in x is expected to show a large correlation with the relaxation of the FeO₆ octahedron distortion.

To clarify the correlation between the crystal structure and magnetic structure of Nd1-xSrxFeO3 (0.1 ≤ x ≤ 0.9) in more detail, powder neutron diffraction (PND) data of the Nd_1-xSr_xFeO₃ (0.1 ≤ x ≤ 0.9) samples were collected at room temperature with the medium resolution neutron powder diffractometer (MEREDIT), part of the CANAM infrastructure, at the Nuclear Physics Institute, Czech Republic. All Rietveld refinements were carried out using the GSAS-Ⅱ suite of programs [1].

It is confirmed that the FeO6 octahedron distortion is relaxed as x increases and approaches the crystal structure of the pseudo-cubic. Fig 1 shows the evolution of Fe-O-Fe angles with x in Nd_1-xSr_xFeO₃ (0.1 ≤ x ≤ 0.9).

The materials present antiferromagnetic order, with magnetic moment of Fe decreasing from ~ 3.2 µB for x = 0.1 to ~0.2 µB for x = 0.9. With 0.1 ≤ x ≤ 0.4, the magnetic spins are oriented in the c-axis direction (BNS Magnetic Space Group: Pn'ma'), while for 0.5 ≤ x ≤ 0.9 they appear to be in the a-axis direction (BNS Magnetic Space Group: Pnma). The magnetic structures for Nd_0.9Sr_0.1FeO₃ and Nd_0.5Sr_0.5FeO₃ are shown in fig 2. Crystal and magnetic structures were drawn using VESTA [2].

Low-dimensional magnetic crystals display highly anisotropic interactions between the magnetic moments, yielding interesting magnetic [1], electronic [2], and optical properties [3]. The ground and excited states of low-dimensional magnetic systems attract interest with increasing spin dimension andor decreasing spin values [4]. Materials containing isolated chains might work as models for (1D) S=1/2 Heisenberg systems and Ising spin chains. These models can be used for shedding light on the understanding of magnetic exchange interaction in highly correlated systems. When a geometrical distribution of the magnetic moments is such that it constrains the exchange interactions, the interaction energy is difficult to be minimized, causing the appearance of a complex electronic structure. This often leads to magnetic frustrations. Magnetic frustrations have an impact beyond magnetism, such as multiferroic and high-temperature conductivity behaviors [5,6]. Intermetallic systems are prone to have magnetic frustration, having a high potential for finding new electronic phenomena [7]. The system R₂TGe₆ often displays complex modulated magnetic structures, which can be elucidated by neutron scattering, while the nuclear structure is solved by X-rays or electron diffraction. The accurate structure elucidation of complex magnetic structures is crucial for understanding these structures. Currently, the sole program that handles complex magnetic structures and can combine X-ray, electron, and neutron diffraction is Jana2006 [8]. New features for the analysis of complex magnetic structures are being developed and require neutron diffraction data of such structures. We synthesized some of the compounds from the R₂TGe₆ system, aiming at acquiring neutron diffraction data for testing and further developing the new tools for magnetic structures in Jana2006.

[1] W.-X. Zhang, R. Ishikawa, B. Breedlove, M. Yamashita. (2013), RSC adv. 3, 3772.

[2] G. C. Xu, W. Zhang, X. M. Ma, Y. H. Chen, L. Zhang, H. L. Cai, Z. M. Wang, R. G. Xiong, S. Gao. (2011) J. Am. Chem. Soc. 133, 14948.

[3] A. Kandasamy, R. Siddeswaran, P. Murugakoothan, P. S. Kumar, R. Mohan. (2007) Cryst. Growth Des. 7, 183.

[4] A. P. Ramirez. (1994) Annu. Rev. Mater. Sci. 24, 453.

[5] M. Mostovoy. (2008) Nature Mater. 7, 269.

[6] P. W. Anderson. (1987) Science 235, 4793.

[7] S. Arsenjević, J. M. Ok, P. Robinson, S. Ghannadzeh, M. I. Katsnelson, J. S. Kim, N. E. Hussey. (2016) Phys. Rev. Lett. 116, 087202.

[8] V. Petřiček, M. Dušek, L. Palatinus. (2014) Z. Kristallogr. 229, 345.

This work was financially supported by the project Mobility MSM100102001 of the Czech Academy of Sciences and by the Project 19-07931Y of the Czech Science Foundation.

Metal-organic frameworks (MOFs) are hybrid (organic/inorganic) crystalline porous solids intensively studied for their potential applications in different domains related to energy, environment or health [1]. Diffraction-based techniques are one of the major methods for the crystal structure determination of MOFs, providing a better understanding of their unique properties. However, the information obtained is the averaged periodic structure, while in some cases - such as adsorption and catalysis - the local structural features (ie., crystal surfaces, interfaces, the presence of guest molecules or defects) are key elements, which can be visualized using high-resolution TEM methods. However, MOFs are among the most beam-sensitive materials and can be easily damaged after exposure to a few electrons/Ų. Therefore, only few successful studies of HRTEM imaging were reported, so far, focusing on just a handful of MOFs [2]. These recent studies have demonstrated that using a direct detection electron counting camera (DDEC) allows performing HRTEM imaging of MOFs with extremely low dose rates (as low as 4 e^-/Ų.s). Thus, individual inorganic clusters could be visualised, while in some cases, the organic linkers could be also resolved [3].

The prediction of the electron-beam stability of a MOF nanocrystal is a difficult task since many structural, morphological or instrumental parameters might be taken into account and could have interconnected effects (Figure 1a). This work aims at identifying the most prominent parameters and assessing their influence on the stability of these objects when exposed to the beam and under given operating conditions. Several known MOFs were imaged by low-dose HRTEM (Figure 1b) enabling the investigation of the effect of the voltage, the particle size and orientation, the presence of guest molecules, as well as the nature and the geometry of the organic and the inorganic moieties. The threshold cumulative electron dose that a MOF can withstand before being completely damaged is determined by monitoring the fading of the spots on the fast Fourier transform images calculated after different exposure times. It has been found that the size of the particle does not have as much impact on the stability as its orientation and its degree of crystallinity, while the presence of guest species encapsulated in the pores has been found to significantly improve the stability. The comparison of the lowest and highest threshold electron doses measured for particles oriented along random off-zone axes of a series of aluminium-based and titanium-based MOFs (Al-MOFs and Ti-MOFs) is given in Figure 1b. The obtained results and the influence of the different features and parameters (ie., linker connectivity, nuclearity of the inorganic building unit, the oxidation state of the metal ions, etc.) on the electron beam stability of these MOFs will be presented. Besides, low-dose HRTEM imaging realised on new in-house MOFs and its use for structure resolution will be also highlighted.

A novel lectin was isolated, purified and characterized from seeds of Entada rheedii using ammonium sulphate precipitation followed by lactose affinity chromatography. On SDS-PAGE, the purified Entadin lectin appeared as a single band (monomer in nature) with a molecular mass of approx. 20 kDa both in reducing as well as in non-reducing conditions. Mass spectroscopic analysis confirms the molecular weight of Entadin lectin as 19333 Da. Entadin lectin showed highest titer value in agglutination against human blood group-B RBC and its Hemagglutination activity was inhibited by lactose, cellobiose, and galactose only. Periodic Acid Schiff’s (PAS) stain confirmed the glycoprotein nature of Entadin lectin with an approx. 5 % of carbohydrate content. The lectin is highly stable even after incubation at a wide range of temperatures (30 to 60 °C) and pH (6 to 10). Antiproliferative effect of Entadin lectin against lung cancer cells A549 and cervical cancer cells HeLa showed IC₅₀ value of 38 µg/mL and 34 µg/mL and no anti-proliferative activity against normal cells. Cell morphological studies revealed that Entadin lectin induced apoptosis both in A549 and HeLa cancer cells which was confirmed by (AO/EB) and Hoechst (33258) nuclear counter staining. Further, Lectin was crystallized using the hanging-drop vapour-diffusion method with 30% PEG 8000 as precipitating agent, 0.2 M ammonium sulphate and 0.1 M sodium cacodylate pH 6.5.

Ternary coordination compounds of copper with amino acids / amino acid derivatives and heterocyclic bases are important in studies related to the biological activity and structural properties. They have potential application in biomedicine and crystal engineering [1,2]. Ternary coordination compounds with amino acids and heterocyclic bases as ligands possess many hydrogen bond acceptors and donors and form diverse but somehow predictable supramolecular motifs based on covalent bonds or noncovalent interactions (porous structures, coordination polymers or other arhitectures) [3,4].

As a part of our ongoing investigation of copper–amino acidato systems, we report 5 new crystal structures of ternary coordination compounds of copper(II) with 1,10-phenanthroline (Phen) and L-threonine (Thr) and sarcosine (Sar): [Cu(Sar)(H₂O)(Phen)][Cu(SO₄)(Sar)(Phen)]·Py·2H₂O (1), [Cu(Sar)(H₂O)(Phen)][Cu(SO₄)(Sar)(Phen)]·7H₂O (2), [Cu(Sar)(H₂O)₂(Phen)][Cu(Sar)(H₂O)(Phen)]SO₄·8H₂O (3), {[Cu(m-Thr)(Phen)]₂SO₄·3.5H₂O}_n (4), [Cu(Thr)(H₂O)(Phen)] [Cu(Thr)(Py)(Phen)]SO₄·2H₂O (5); (Py = pyridine). Except for one complex cation in compound 3 as well as in the coordination polymer 4, the copper(II) ion is pentacoordinated by N, O-donating Thr or Sar ligand and N, N’-donating Phen ligand in the basal plane, and apically coordinated by a solvent molecule (water or pyridine) or sulphate anion. In one of complex cation in 3 the copper(II) ion is octahedrally coordinated with Sar and Phen ligands in the equatorial positions and two water molecules in the axial positions. Compound 4 is a coordination polymer with the copper(II) ion pentacoordinated by didentate Thr and Phen ligands while the axial position is occupied by a carboxylate oxygen atom from the neighbouring complex unit. In all crystal structures infinite double chains are formed through π-interactions of the neighbouring Phen rings, which are interconnected by extensive network of O–H∙∙∙O, N–H∙∙∙O and/or O–H∙∙∙N hydrogen bonds. Except for compound 5, solvents molecules of crystallization are located in 1D channels (Figure 1.a). In 5 the water molecules of crystallization are located in pockets between double chains, and with sulphate ions serve as hydrogen bond bridges between adjacent chains through O–H∙∙∙O and N–H∙∙∙O hydrogen bonds (Figure 1.b).

The cytotoxicity of coordination compounds was investigated on cultured HepG2 (human liver cancer) and THP-1 (human leukemia monocytic) cell lines. The compounds showed prominent cytotoxicity towards both cell lines.

a)

b)

Figure 1. a) 1D channels of solvent molecules in 1, b) pockets of water molecules in 5.

[1] Lakshmipraba, J. et al. (2011) European Journal of Medicinal Chemistry, 46, 3013–3021.

[2] Zhang, S. &. Zhou J. (2008) Journal of Coordination Chemistry 61(15), 2488–2498.

[3] Vušak, D. et al. (2017) Cryst. Growth Des. 17, 6049–6061.

[4] Maji, T. K. (2007) Pure Appl. Chem. 79(12), 2155–2177.

Zeolites are crystalline microporous materials of great interest not only from an academic point of view but also from an industrial point of view due to their properties and multiple applications. These properties largely depend on its chemical composition but also on its structure. At present, the International Zeolite Association (IZA) has accepted 242 different structures [1], each with specific characteristics and a particular crystal structure. Obtaining one or the other structure is highly influenced by the organic structure directing agents (OSDAs) used during the synthesis.

Although the most typical OSDAs consist of alkylammonium cations, molecules containing phosphorous or sulfur atoms instead of nitrogen have also been described in recent years. Recently, our group also described the use of alkylarsonium cations, where nitrogen is replaced by an arsenic atom, which effectively lead to the formation of a zeolitic structure [2].

The use of As in ADE provides some additional benefits, since it allows the incorporation of heavy atoms that can act as a probe for different studies of the materials obtained. Its high electron density, compared to that of nitrogen, allows its easy location even using laboratory X-ray powder diffraction equipment; to date, the location of alkylammonium cations often requires the use of single crystal techniques or the use of complex methods. Furthermore, this substitution of N for As allows the use of other advanced characterization techniques, such as nuclear magnetic resonance MAS-NMR of ⁷⁵As in the solid sample, or X-ray absorption spectroscopy (XAS) at the K border of As, to analyze the location and properties of the molecule within the zeolitic network and its evolution under non-standard conditions.

[1] http://www.iza-structure.org/databases/

[2] Sáez ‐ Ferre S., Lopes Ch.W., Simancas J., Vidal ‐ Moya A., Blasco T., Agostini G., Mínguez Espallargas G., Jordá JL, Rey F. and Oña ‐ Burgos P. (2019) Use of Alkylarsonium Directing Agents for the Synthesis and Study of Zeolites. Chemistry - A European Journal 25, 16390-16396

Keywords: zeolite; alkylarsonium; diffraction; XAS; NMR

The authors acknowledge the funding of the Severo Ochoa SEV-2016-0683 and Maria de Maeztu MDM-2015-0538 programs. S.S-F thanks the MEC for its Severo Ochoa Scholarship SPV-2013-067884. P.O.-B. and G.M.E. They thank the MEC for their Ramón y Cajal contracts (RYC-2014-16620 and RYC-2013-14386). The authors are grateful for the financial support of the Government of Spain (RTI2018-096399-A-I00, RTI2018-101784-B-I00 and CTQ2017-89528-P) and Generalitat Valenciana (PROMETEO / 2017/066). The UPV's Electronic Microscopy Service is thanked for its help in the characterization of samples. We thank the synchrotron ESRF for assigning the beam time (proposal CH-5193), the Italian CRG beamline in ESRF (LISA-BM08) and Alessandro Puri for help and technical support during our experiment. C.W.L. thanks CAPES for a predoctoral fellowship (Science without Frontiers - 13191 / 13-6).

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are two highly representative per- and polyfluoroalkyl substances (PFAS) recognized as environmental persistent organic contaminants [1-2]. Adsorption on zeolites is a reliable alternative to eliminate these compounds from water and wastewaters because of their framework flexibility, high organic contaminant selectivity, high specific capacity, rapid kinetics, excellent resistance to chemical, biological, mechanical or thermal stress [3-4]. Ag-exchanged zeolites show unique physical, chemical, and antibacterial properties along with strong absorption property and good stability thus working synergistically in removal of PFAS from water. Consequently, a deep investigation of these materials with exceptional performances must be explored beside their effectiveness for PFAS removal. In this work, the interactions between PFOA and PFOS and Y zeolites (FAU-topology) with different SiO₂/AlO₂ (SAR) were systematically investigated for the first time, in order to evaluate the role of hydrophobic and electrostatic forces in the interaction between polyfluoroalkyl substances and the adsorbents. A careful characterization of Y zeolites (with SAR= 30, 60 and 500, respectively) loaded with PFOA and PFOS, respectively, was carried out before and after silver functionalization in order to: i) investigate the effectiveness of synthetic Y and Ag-Y zeolites with a different SAR ratio towards PFAS, ii) characterize their structure; iii) localize the host species in the zeolites channel system, iv) investigate the thermal stability and their crystallinity degree, v) probe the interaction between PFAS molecules, water molecules, Ag ions and framework oxygen atoms. X-ray powder diffraction patterns (XRD) of the as-synthesized and Ag-loaded Y samples before and after PFAS adsorption, were collected at room temperature by using Bruker D8 Advance Diffractometer with a Sol-X detector, Cu Kα1, α2 radiation. Rietveld structure refinements were performed using the GSAS package with EXPGUI graphical interface in the Fd-3m space group. The zeolites crystallite sizes were achieved by both the Scherrer and Williamson-Hall approaches. TG and DTA measurements of all samples were performed in constant air flux conditions from room temperature up to 1400 °C using an STA 409 PC LUXX® - Netzsch (10 °C/min heating rate). After PFOS and PFOA adsorption, the selected materials maintain a high crystallinity degree. PFASs adsorption on Y and AgY samples was evidenced by differences in both the positions and intensities of the powders diffraction peaks, which are indicative of structural variations in terms of nature and concentration of the extraframework species, unit cell dimensions and framework geometry. The PFOA and PFOS adsorption was accompanied by deformations of the framework, evidenced by the value of the crystallographic free area of the zeolites channel systems. In all samples, PFOA and PFOS molecules were localized at the centre of Y-supercage, thus assuming six different orientations. The bond distances indicated strong interactions mediated via water molecules between zeolite framework and PFASs reactive carboxylic and sulfonyl functional groups. The structure refinements gave an extraframework content corresponding to ~26.0 and 22.0% wt. of PFOA and PFOS, respectively, in good agreement with the weight loss given by the thermogravimetric analyses. Our results highlighted that Ag-exchanged zeolites with high SAR were the most efficient adsorbents thus representing selective tools for PFOS and PFOA abatement as environmentally friendly, bactericidal and low-cost materials.

[1] Sinclair, G.M., Long, S.M., Jones, O.A.H. (2020). What are the effects of PFAS exposure at environmentally relevant concentrations? Chemosphere, 258, 127-340[2] Pan, C., Liu, Y., and Ying, G. (2016). Perfluoroalkyl substances (PFASs) in wastewater treatment plants and drinking water treatment plants: removal efficiency and exposure risk. Water Research. 106, 562-570.[3] Gagliano, E., Sgroi, M., Falciglia, P.P., Vagliasindi, F.G.A., Roccaro, P. (2020). Removal of poly- and perfluoroalkyl substances (PFAS) from water by adsorption: Role of PFAS chain length, effect of organic matter and challenges in adsorbent regeneration. Water Res. 171, 115-381.[4] Mingshu, L., Yujie, R., Ji, W., Yuanhui, W., Jieyu, C., Xinrong, L. and Xiaoyan, Z. (2020). Effect of cations on the structure, physico-chemical properties and photocatalytic behaviors of silver-doped zeolite Y. Microporous and Mesoporous Materials, 293, 109-800.

Identification of agrochemical degradation metabolites occurring in soil, water, and crops, and assessment of their toxicity are of great importance in view of food safety. A common approach to identify the structures of unknown metabolites is to synthesize their canditdates as reference standards based on the structures estimated from chemical information obtained from nuclear magnetic resonance (NMR) and mass spectrometric (MS) analyses, and to compare the unknown metabolites with the reference standards.

However, agrochemical degradation metabolites are usually obtained in only very small amounts, and a multitude of structures can occur in the environment and crops. Therefore, synthesizing all such potential metabolites and similar candidate compounds involves extremely time- and money-consuming efforts. If the molecular structures of a wide range of metabolites with very small amount can directly be determined by single crystal X-ray (SCX) analysis, the time and economic costs will dramatically be reduced.

The crystalline sponge (CS) method is a novel technique for sample preparation of SCX developed by Prof. Fujita.[1] The CS method utilizes a crystal of metal-oraganic framework (MOF) as a crystalline molecular container that can incorporate a wide variety of small molecules within the pores and arrange the molecules in a regular pattern according to the periodicity of the host crystal. As a result, the host-guest complex as a whole can be regarded as a single crystal.

The CS method is very advantageous for structure determination of the agrochemical degradation metabolites. Crystal preparation using one crystal of MOF enables trace analysis with a sub-microgram scale. As no other approach is able to produce accurate structural determinations with just micrograms of unidentified sample purified by preparative HPLC, based on degradation/metabolism experiments on a laboratory scale, SCX analysis combined with the CS method thus offers the potential of dramatically changing the conventional modality of degradation metabolite analysis.

In this presentation, we will show the initial examples of the structure identification of agrochemical metabolites (Fig. 1).

Metal-organic frameworks (MOFs) have attracted widespread attention for their porosity and potential applications in separation chemistry, catalysis, molecular sensing and gas storage. [1] This class of materials are coordination polymers and may be 1-periodic, 2-periodic or 3-periodic. Firstly, we report a partially-fluorinated, 2-periodic MOF, [Zn(hfipbb)(bpt)]_n·n(C₃H₇NO)₂·n(H₂O) where H₂hfipbb = 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) and bpt = 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole. This framework undergoes single-crystal-to-single-crystal in solvent exchange with ethanol, dichloromethane and N,N’-dimethylacetamide, respectively. The solvent-induced ‘breathing’ of the 2-periodic frameworks results in potential void spaces varying from 15.2-35.4%.[2] In addition, we report the synthesis of a pair of isoreticular mixed-ligand MOFs, [Zn(μ₂-ia)(μ₂-bpe)]_n·nDMF and [Zn(μ₂-mia)(μ₂-bpe)]_n·n(C₃H₇NO), where ia = isophthalate, mia = 5-methoxyisophthalate and bpe = 1,2-bis(4-pyridyl)ethane.[3] Both structures consist of doubly interpenetrated 2-periodic frameworks. Despite a lower void space, one of the activated MOFs exhibits significantly higher sorption of carbon dioxide at 195 K, illustrating that small changes in functional groups, even in structurally similar MOFs, may have a large effect on sorption properties.

[1] Zhou, H.; Long, J. R.; Yaghi, O. M. Introduction to Metal-Organic Frameworks. Chem. Rev. 2012, 112, 673-674.

[2] Chatterjee, N. and Oliver, C.L., Cryst. Growth Des. 2018, 18, 7570−7578.

[3] Gcwensa, N., Chatterjee, N., Oliver, C.L., Inorg. Chem. 2019, 58, 2080−2088.

A new approach to time-resolved X-Ray experiments implementation at both laboratory X-Ray sources and synchrotron facilities is presented. Proposed X-Ray diffraction method is based on adaptive X-ray optics and applied for investigation of irreversible deformation processes in crystalline materials under external loading with time resolution. This method allows receiving information about changes in atomic structure recording rocking curves (dependence of X-ray radiation intensity in the vicinity of Bragg angle) and reciprocal space maps (RSM) by fast tunable X-Ray optical element. This element consists of a piezoelectric monolithic bimorph lithium niobate (LiNbO3) single crystal and a silicon plate attached to its face. When electrical signal is applied to the lithium niobate, it is possible to control the spatial position of the diffracted X-ray beam [1]. Time resolution of proposed method scales up to milliseconds for rocking curve record and up to hundreds of milliseconds in RSM case, and mainly depending on brilliance of X-ray.

The presented approach makes it possible to obtain information about changes in crystal structure with a lower time delay compared to existing methods [2].

The evolution of the defective structure of crystalline materials subjected to controllable and measured uniaxial mechanical compression (load up to MPa range) was investigated using the proposed method. The essence of such evolution is defect multiplication, displacement and shifting of atomic planes, which can be easily determined by changes in rocking curve and RSM parameters. This structural process is of great interest, as it is possible to observe defects behavior in a crystal during elastic deformation with time resolution.

The reported study was funded by RFBR and DFG 19-52-12029 and by RFBR according to the research project №18-32-20108.

Transition metal oxides with the perovskite crystal structure constitute a class of materials long considered highly interesting for research in structure-property relationships and materials design. In this work we consider the B cation rock salt ordered double perovskite structure, with general formula A₂BB´O₆. We are interested in the magnetically frustrated fcc B’ cation sublattice, where on the B´ position we have placed Rh 4d⁵ as a reduced SOC analogue in the context of our previous iridate double perovskite work.

We have synthesized La₂BRhO₆ (B = Zn, Mg) compounds as powders and single crystals that form in the P2₁/n space group. Their structure and properties have been characterized with a combination of XRD, SQUID magnetometry, and heat capacity. Interestingly, the materials exhibit no long range order to very low temperatures, and may host an exotic magnetic ground state.

Metal-organic frameworks (MOFs) are an emerging class of crystalline materials made by connecting a metal ion or cluster to polytypic organic linkers. They have a wide range of potential applications in gas storage, catalysis, drug delivery, sensing, separation, and magnetism [1, 2]. Single crystal to single crystal (SC-SC) transformation is a phenomenon where significant changes in the crystal structure occur in the solid state without destroying the integrity of the crystal such that it can still be analyzed by means of X-ray diffraction. Single crystal transformations are important for the development of new and technologically useful materials including devices and sensors.

Recently, we synthesized the MOF, {[Co(34pba)₂(OH₂)](DMF)_0.5(H₂O)}_n (A)_, DMF= N,N-dimethylformamide, 34pba= with water and DMA using solvothermal method. X-ray analysis revealed that A crystallises in the Triclinic, system with space group of P-1. Further studies revealed that A is a dynamic material which can be used for sensing [3].

In this work, we present the solid state studies in A and DMF using solvothermal methods. They were fully characterized using X-ray diffraction methods, infrared spectroscopy, elemental analysis and thermal methods.

[1] Kuppler R., Timmons D., Fang Q., Li J., Makal T., Young M., Yuan D., Zhao D., Zhuang W., Zhou H., (2009), Coord. Chem. Rev., 253, 3042

[2] Farha O. and Hupp J., (2010), Accounts of Chem. Rese., 43, 1166

[3] Dzesse Tekouo. C. N., Emmanuel N. Nfor and Susan A. Bourne,( 2018), Crystal growth & Des., , 18(1), 416.

Square planar rhodium(I) complexes of the type [Rh(L,L’-Bid)(CO)(PPX₃)], where L,L’-Bid = monoanionic bidentate ligands and PPX₃ are tertiary phosphine ligands, have been extensively investigated as potential catalyst precursors in different conversion reactions. ^{[1],[2],[3],[4],[5]}

The main objective of this study is to use solution and solid-state ³¹P NMR spectroscopy in conjunction with X-ray crystallography to investigate the structure and reactivity relationship of the rhodium(I) complexes for potential application in catalysis.

A range of complexes of the type [Rh(L, L’-Bid)(CO)(PPX₃)] with systematic manipulation of the steric and electronic properties were synthesized and characterized using IR, UV/Vis, and NMR spectroscopy. These rhodium(I) complexes were obtained from the substitution of one carbonyl ligand in the complexes [Rh(L,L’-Bid)(CO)₂], by simple stoichiometric reaction with monodentate tertiary phosphines. Correlations of different parameters such as the first-order coupling constant ¹J_Rh-P, chemical shift, and the Rh-P bond distances were evaluated in order to understand the coordination environment around the metal center.

[1] A. Roodt, H.G. Visser, A. Brink. Crystallogr. Rev. 17 (2011) 241-280.

[2] S. Warsink, F.G. Fessha, W. Purcell, J.A. Venter, J. Organomet. Chem. 726 (2013) 14-20.

[3] M. M. Conradie, J. Conradie, Dalton Trans. 40 (2011) 8226-8237.

[4] A. Brink, A. Roodt, G. Steyl, H.G. Visser, Dalton Trans. 39 (2010) 5572–5578.

^[5] P.P Mokolokolo, A. Brink, M. Schutte-Smith, A. Roodt. J. Coord. Chem. 73 (2020) 2740.

A new metal pyrophosphate, formulated as [(H₂O)₂Co₂(N₂H₅)₂(HP₂O₇)₂] has been synthesized using wet chemistry and investigated by single crystal X-ray diffraction. The compound crystallizes in the triclinic system (S.G: P) with the following parameters (Å, °): a=7.2957(6), b=7.3932(4), c=14.7194(8), α=85.717(4), β=83.703(6), γ=79.710(5). The crystal packing consists of layers parallel to bc plane. These layers are joined by strong hydrogen bonds, building up a three-dimensional infinite network. The structural analysis was coupled with Hirshfeld surface analysis to evaluate the contribution of the different intermolecular interactions to the formation of supramolecular assemblies in the solid state. This analysis revels that the main contributions are provided by the O···H, H···H and Co···O interactions that represent ~85% of the total contributions to the Hirshfeld surface. Pyrophosphate group show bent eclipsed conformation which was confirmed by IR spectroscopy. Its Thermal behaviour consists mainly of the loss of hydrazine moieties and water molecules leading thus to the formation of an anhydrous cobalt diphosphate. The condensed phosphate exhibits a promising catalytic activity in the oxidation and decomposition of methylene blue dye with hydrogen peroxide under ambient conditions only for 2 hours.

Currently, a significant area of materials science concerns the development of mechanisms for controlled variation of a material’s structure through local defects formation. This ensures the adjustment of a material’s structural organization and functional properties for application in novel data storages, sensors, and energy accumulation systems, among others.

The near-surface structural variation has been found in SrTiO₃ [1] and in TeO₂ single crystals as well. It is caused by the migration of oxygen vacancies in an external electric field. The dynamics and anisotropy of the formation process of near-surface structures in paratellurite (α-TeO₂) single crystals due to the migration of charge carriers induced by an external electric field are studied by the in-situ X-ray diffraction (XRD) technique and electrical conductivity measurements.

Single crystal diffraction patterns exhibit an interesting response on an external electric field. The observed effect manifests itself in the diffraction rocking curve (DRC) parameters and its shape variation with a reversible character [2]. This is explained by the formation of the strain field (domains) with a small mutual angular misorientation. The threshold field strength about 100 V/mm, above which the broadening of the XRD reflection peak starts, has been revealed. A linear dependence of the broadening value on the applied field strength has been determined.

A diffraction peak broadening occurs for both polarities with a simultaneous shift of its maximum only occurring on the surface with a positive electric potential [3]. For the (110) crystal cut, a much higher saturation time (800-1000 s) of the process compared to the (100) cut (~300 s) is registered. Moreover, in all cases, the relaxation is almost 2–3 times faster than the saturation, thereby repeating the character of the measured electrical conductivity. The electric field application along the fourth-order axis [001] doesn’t lead to visible changes in the diffraction peak parameters.

A thickness of the layer with a strain formed close to the surface is estimated by XRD at different diffraction orders [4]. The experimental data is compared with the results of DRC simulation considering the crystal lattice deformation with the depth attenuation. The simulation shows the strain localization depth of 3.6 μm for the (110) crystallographic cut, whereas the diffraction peak profile for the (100) cut is suitably described by a layer with a thickness of 1.6 μm.

Calculation according to the electrical measurements shows that the Debye screening layer of charge is localized at the same characteristic length. The concentration of defects in the near-surface region is inversely dependent on the screening length and reaches the value of 1.3×10²² m⁻³, which is three orders of magnitude greater than vacancies concentration in the bulk.

[1] Hanzig, J., Zschornak, M., Hanzig, F., Mehner, E., Stöcker, H., Abendroth, B., Röder, C., Talkenberger, A., Schreiber, G., Rafaja, D., Gemming, S., & Meyer D. C. (2013). Physical Review B 88, 024104.
[2] Kovalchuk, M. V., Blagov, A. E., Kulikov, A. G., Marchenkov, N. V. & Pisarevsky, Yu. V. (2014). Crystallography Reports 59(6), 862.
[3] Kulikov, A. G., Blagov, A. E., Marchenkov, N. V., Lomonov, V. A., Vinogradov, A. V., Pisarevsky, Yu. V. & Kovalchuk, M. V. (2018). JETP Letters 107(10), 646.
[4] Kulikov, A. G., Blagov, A. E., Ilin, A. S., Marchenkov, N. V., Pisarevsky, Yu. V. & Kovalchuk, M. V. (2020). Journal of Applied Physics 127, 065106.

Keywords: near-surface structure; electrical double layer; charge carriers’ migration; X-ray diffractometry

This work supported by the Ministry of Science and Higher Education within the State assignment FSRC Crystallography and Photonics RAS in part of “crystal growth and sample preparation” and by the Russian Foundation for Basic Research (Project No. 19-52-12029 NNIO_a), part of “investigation of the paratellurite crystal structure rearrangement under the electric field influence”.

Mechanically responsive organic materials have attracted attention from perspective of both basic research and applications in smart actuators and soft robots [1]. We have developed many mechanical crystals such as azobenzene [2] and salicylidenealine [3], mainly based on photoisomerization. However, photoisomerization has some disadvantages for crystal actuation, such as a limited number of photoisomerizable crystals, slow actuation speed, and no actuation of thick crystals. Here we report photothermally driven fast-bending actuation and simulation of a salicylideneaniline derivative crystal with an o-amino substituent in enol form (enol-1).

X-ray crystallographic analysis revealed that enol-1 crystal belonged to the space group, P2₁, showing that the enol-1 molecule is achiral but forms chiral crystal. The molecules were connected weakly through the intermolecular hydrogen bond chains in a two-fold helical manner to form the herringbone structure along the b axis (Figure 1a, b). Absorption spectra of a thin enol-1 crystal revealed that enol-1 crystal exhibited fast photoisomerization from enol to trans-keto form (τ=0.9 s) by UV light and fast back-isomerization (τ=4.2 s) from trans-keto to enol form.

Under UV light irradiation, the thin (<20μm) crystals bent away from the light source quickly (in a few seconds) by photoisomerization. In contrast, the thick (>20μm) crystals bent very quickly (in several milliseconds) due to the photothermal effect, finally achieving 500-Hz high-frequency bending by pulsed UV laser irradiation. We propose a possible mechanism in which photothermally driven bending is caused by a non-steady temperature gradient in the thickness direction. The temperature gradient was calculated based on a one-dimensional non-steady heat conduction equation, resulting in the successful simulation of bending via the photothermal effect and the elucidation of the proposed mechanism (Figure 1c). Most materials that absorb light show their own photo-thermal effects. The creation of crystal motion via the photothermal effect will expand the designability and versatility of mechanical crystals in the future.

[1] Koshima, H. (2020). Mechanically Responsive Materials for Soft Robotics, ed. H. Koshima, Wiley-VCH, Weinheim.

[2] Koshima, H., Ojima, N., Uchimoto, H. (2009). J. Am. Chem. Soc. 131, 6890–6891.

[3] Koshima, H., Takechi, K., Uchimoto, H., Shiro, M., Hashizume, D. (2011). Chem. Commun. 47, 11423–11425.

One of the most striking phenomena in nanoscience is the formation of self-assembled structures. Metal doped TiO₂ nanocrystals (NCs) display varying physiochemical properties based on their composition and structure. For instance, TiO₂ NCs made of a doped core have different photocatalytic properties than that doped core encased with a shell layer. This work discusses the choice of aliovalent Scandium (Sc) dopant in anatase host-lattice and the development of NCs with new core/shell morphology as a function of Sc diffusion and segregation during heat treatment of precipitated precursor from 200 to 1000 °C.

Rietveld's refinement of powder X-ray diffraction patterns [1] confirmed that Sc (with a low dopant ratio of 4 at. %) is incorporated into a TiO₂ lattice at temperatures up to 800 °C. It was found that doping with Sc caused lattice stresses and structural defects (vacancies) due to misfit strain energy resulting from different ionic radii between Sc³⁺ (0.745 Å) and Ti⁴⁺ (0.605 Å). Annealing at 800 °C under air generated segregation of Sc into specific regions of NCs. This phenomenon can be explained by simultaneously diffusion and segregation processes of Sc dopant into a thin shell surrounding the TiO₂ core while maintaining to reduce the energy of the Sc-Ti-O system. To investigate the impact of Sc on the NCs morphology, complementary scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were employed.

Figure 1a-b shown the core/shell growth of well-crystallized adjacent NCs. The corresponding FFTs (Fig.1b₁) shown the anatase (101) plane, connected to anatase indexed as (1 0 1), (103) and (112) (Fig.1b₂). The EELS profiles across the grain boundaries (GBs) were acquired to estimate the distribution of Sc dopant. Enrichment of the Sc at the shell near the GBs was observed (Fig.1c-d). The segregation shell was estimated to be on the order of a few nanometres.

Evaluation by STEM and EELS showed that the strain-energy driving process can be responsible for the energetically favored core-shell morphology transformation in Sc doped TiO₂ because of the relaxation of strain during NCs growth. The findings could be beneficial to understand the separated stages of NCs' nucleation and growth.

Zirconia based materials possess a unique set of attractive properties, which are responsible for the many applications in which they are used [1]. Some of these involve the use of thin films, whose properties are highly dependent on synthesis and deposition methods. Major changes in the Zr-O phase diagram, thus in material properties, occur when the crystallite size is reduced down to the nanoscale. A good example is that cubic or tetragonal phases, that have better mechanical properties than the monoclinic phase, can be retained in nanocrystalline zirconia [2,3]. The addition of yttria to zirconia can also lead to the stabilization of the high symmetry phases, producing the well-known yttria stabilized zirconia (YSZ). YSZ is the most widely used electrolyte in solid oxide fuel cells (SOFC) due to its high and pure ionic conductivity above 800 °C. However, such high operation temperatures result in high degradation rate for the SOFC, which increases the cost of this technology. Different strategies have been proposed to lower the SOFC operating temperature, being one appealing approach to employ dense thin-film based electrolytes [4].

For this work we synthetized ZrO₂ and 8YSZ (zirconia stabilized with 8% mol of yttria) by the sol-gel method and deposited thin films by dip-coating on glass substrates. The thin film crystallization process was studied in situ by grazing incidence X-Ray diffraction (GIXRD) at the KMC-2 beamline of the BESSY II synchrotron light source of Berlin by varying temperature between 300 and 800 °C in steps of 20 °C, coupled with electrical measurements using the 2-probe method.

Synthesized thin films have thicknesses between 100 and 200 nm. The in situ study on YSZ, presented as example in Figure 1, allowed us to determine how the nano crystallite size of the thin film evolved from 4 nm at 363 °C to 40 nm at 792 °C. The simultaneously measured resistivity enabled us to correlate temperature dependant transport and structural properties of these films. In both ZrO₂ and YSZ thin films, highly symmetric phases (tetragonal and cubic, respectively) are retained at high temperature and after cooling.

Gas sensing is primarily considered as a surface property of materials. The surface structure however depends to a large extent on bulk crystal structure. Knowledge of surface structure in combination with the knowledge of bulk crystal structure is thus helpful in improved understanding of the surface properties of materials. In the present work, vanadium doped tin oxide samples Sn_1-xV_xO₂ (x= 0, 0.304 and 0.343) have been synthesized by simple precipitation methods. All samples have exhibited ppm level ammonia sensing property. Doped samples have been found to be more sensitive to ppm level ammonia in air in comparison to pristine SnO₂. In order to understand the enhancement in ammonia sensing property due to vanadium doping, all samples have been characterized extensively by X-ray diffraction and X-ray photoelectron spectroscopy. Bulk crystal structures of the samples have been established by Rietveld refinements [1] using high quality powder X-ray diffraction data with the aid of the computer program Jana2006 [2]. Surface electronic structures of the samples have been determined by X-ray photoelectron spectroscopy. Analysis of surface electronic states and crystal structures has revealed a direct correlation between surface electron deficiencies and sensing responses. Based on this correlation a model mechanism has been proposed which explains the enhancement in ammonia sensing property of vanadium doped samples in comparison to pure SnO₂ [3].

Figure 1. Schematic of the mechanism for enhancement in gas sensing property

Nirman Chakraborty would like to thank DST INSPIRE (IF170810) for his research fellowship.

Graphene nanopowders and carbon nanotubes (CNTs) are widely synthesized and used to design new electromagnetic interferences (EMI) shielding materials to avoid of the electromagnetic pollution, which increases sharply with unavoidable development of electronics technology [1-2]. EMI can be defined as conducted and/or radiated electromagnetic signals emitted by electrical circuits which, under operation, perturb proper operation of surrounding electrical equipment or cause radiative damage to living/biological species. More generally, electromagnetic shielding is also defined as the prevention of the propagation of electric and magnetic waves from one region to another by using conducting or magnetic materials. The shielding can be achieved by minimizing the signal passing through a system either by reflection of the wave or by absorption and dissipation of the radiation power inside the material [3]. In the present study, the state-of-the-art research was realized in design and characterization of polymer/carbon based composites as nanostructured EMI shielding materials. The newly designed nanographene/CNT doped polymer gels were applied on the fabric substrates (ST, SG, etc. coded) by using spray coating method. The measurements (to determine electromagnetic shielding effectiveness) were performed according to ASTM D4935-10[4]. The prepared materials (before and after the coating) were also structurally investigated in molecular, nanoscopic and microscopic scales by using several complementary experimental (FTIR, WAXS, SAXS, SEM) methods. The obtained form factors which are related to core-shell cylinder and fractal models were used in nanoscale SAXS analyses (Fig.1) to characterize the morphologies, sizes and distributions. Graphen and CNT doping with percentage of 4% shows the comparative results for the layered coatings and EMI Shielding. Mono/multi layer applications of the newly designed nanomaterials on fabrics were also investigated to develope EMI shielding effectiveness. Multilayered topologies are commonly used as liners for all enclosures in which reflection, absorption of waves has to be minimized. The focused studies were increasing the surface area of the nanoparticles and reaching the stabilized monodispersed morphologies and arbitrarily oriented uniform distributions. So the nanoparticle doped polymer matrix coated nanomaterials may behave such as conductive networks against to incident signals. As increasing reflectivity and absorbance results may cause better shielding efficiency. Figure 1. Shielding Effectiveness of 4% Graphene and 4% CNT doped nanocomposite coating layers (Top), 3D, ab-initio structure (DAMMIN) model for %4 CN-ST sample, fitting curve and PDDs (Bottom)

As a result of the study, it was obtained that ellipsoidal fractal units come together to form larger and more compact core-shell oblate shaped nano aggregations. It was also shown that, the size, shape, and distribution-controlled synthesizing processes may be useful and possible to increase electromagnetic shielding effectiveness in the manner of absorption and reflection.

The aspect ratio of the graphene/CNT to polymer is a major parameter and is determinant for the studied samples. Graphene doping is respectively more efficient than that of CNT. The dispersion method is another important factor and must preserve the high aspect ratio of the doped nanomaterials as much as possible within the polymer. Especially, multilayer applications on fabric substrate make reasonably higher shielding effect because of the better surface coverage. With the further experimental works, more efficient results can be obtained with respect to metal doping inside the polymer, in the manner of corrosion, weight load, flexibility and easy application.

TiO₂ fibers were prepared through electrospinning of polymethyl methacrylate (PMMA) and Titanium isopropoxide (TIP) solution followed by calcination of fibers in air at 500 ºC. CTAB protected Palladium nanoparticles prepared through reduction method were successfully adsorbed on the TiO₂ nanofibers. Combined studies of X-ray diffraction (XRD), Scanning electron microscope (SEM) and Transmission electron microscope (TEM), indicated that the synthesized Pd/TiO₂ was anatase phase. BET indicated that the synthesized TiO₂ and Pd/TiO₂ had a surface area of 53.4672 and 43.4 m²/g, respectively. The activity and selectivity of 1 mol % Pd /TiO₂ in the Heck reaction has been investigated towards the Mizoroki-Heck carbon-carbon cross coupling of bromobenzene and styrene. Temperature, time, solvent and base were optimized and catalyst recycled twice. ¹H NMR and ¹³C NMR indicated that stilbene, a known compound from literature was obtained in various Heck reactions at temperatures between 100 ºC and 140 ºC. but the recyclability was limited due to some palladium leaching and catalyst poisoning which probably arose from some residual carbon from the polymer. The catalyst was found to be highly active under air atmosphere with reaction temperatures up to 140 ºC. Optimized reaction condition resulted into 89.7 % conversions with a TON of 1993.4 and TOF value of 332.2 hr^-1

The microstructural characterization of spinel-ferrites has been long discussed in the literature [1]. Such interests are justified by the spinel-ferrites potential applications that involve spintronic and magnetic resonance imaging (MRI), gas sensors, magnetic recording, medical diagnostics, antibacterial agents and self-controlled magnetic hyperthermia [2]. In the present work, we have synthesized Co_xZn_1-xFe₂O₄ spinel ferrite nanoparticles (x= 0, 0.1, 0.2, 0.3 and 0.4) via the precipitation and hydrothermal-joint method. Structural parameters were cross-verified using X-ray diffraction (XRD) and electron microscopy based-techniques. The magnetic parameters were determined by means of vibrating sample magnetometry. The as-synthesized Co_xZn_1-xFe₂O₄ nanoparticles exhibit high phase purity with a single-phase cubic spinel-type structure of Zn-ferrite. The microstructural parameters of the samples were estimated by XRD line profile analysis using Williamson-Hall method. The calculated crystallite sizes from XRD analysis for the synthesized samples ranged from 8.3 to 11.4 nm. The electron microscopy analysis revealed that all powder samples are composed of regular spherical nanoparticles with highly homogeneous elemental composition. The Co_xZn_1-xFe₂O₄ spinel ferrite system exhibits paramagnetic, superparamagnetic and weak ferromagnetic behavior at room temperature depending on the Co²⁺ doping ratio, while ferromagnetic ordering with a clear hysteresis loop is observed at low temperature (5K). We concluded that the substitution of Zn with Co²⁺ ions impact both structural and magnetic properties of ZnFe₂O₄ nanoparticles.[3]

References:

[1] Frajera, G., Isnard, O., Chazal, H.& Delette, G. (2019). J. Magn. Magn. Mater. 473, 92

[2] Samavati, A.& Ismail, A. F. (2017). Particuology. 30, 158.

[3] Mohamed, W. S., Alzaid, M., Abdelbaky, M.S. M., Amghouz, Z., García-Granda, S.& Abu-Dief, A.M.(2019). Nanomaterials.9, 1602.

Keywords: spinel ferrite nanoparticles; hydrothermal method; magnetic parameters; electronmicroscopies; ferromagnetic ordering.

Acknowledgments

Spanish MINECO (MAT2016–78155-C2–1-R) and Gobierno del Principado de Asturias (GRUPIN-IDI/2018/0 0 0170) are acknowledged for the financial support

In the present investigation, silica gels have been synthesized via sol-gel method under microwave radiation. For that, precursor solutions were prepared using tetraethylorthosilicate (TEOS) as the silica precursor, varying the molar ratios of water and ethanol to it. HCl was added before heating to perform acid gelation, while NH₃ (2 M) was added after gelation to promote polycondensation and Ostwald ripening reactions during aging. The use of microwave radiation under these conditions resulted in a favourable effect on the final structure of the polymeric network [1]. This approach makes it possible to obtain mesoporous silica gels in a short time, but amorphous in all cases (Fig. 1). The XRD pattern displayed the presence of a broad peak at 2θ = 17–29° that corresponds to the formation of amorphous silica according to JCPDS-card 96-900-1582.

The magnesio-thermal reduction process has already been reported as a useful way to convert silica into silicon in the presence of magnesium as a reduction agent [2,3]. Thus, our amorphous silica gels were mixed with Mg in a weight ratio of 1:1 and treated at 750 °C for 12 h under an inert atmosphere (Ar, 300 mL/min). Many phases can be produced from the reduction process of SiO₂ and Mg, such as MgO and Mg₂Si. Thus, the reduced samples were subsequently washed with HCl (1 M) for 4 hours to eliminate the undesired secondary phases. The structural properties of the obtained silicon gels were analysed and measured by X-ray diffraction (XRD), X-ray fluorescence (XRF) and high-resolution transmission electron microscopy (HR-TEM). Fig. 1 shows the XRD data of the final reduced silicon gel, illustrating the complete removal of SiO₂, with only Si peaks remaining in the structure. The major diffraction peaks at 2θ = 28.4°, 47.4° and 56.2° are presented at (111), (202) and (131) planes, respectively, which can be attributed to high-purity silicon gel according to JCPDS-card 96-901-3109. Also, the absence of additional peaks indicates that no impurities are present in the structure.

Figure 1. XRD data of a) silica gel before treatment and b) silicon gels after magnesio-thermal reduction.

[1] Flores-López, S.L., Villanueva, S.F., Montes-Morán, M.A., Cruz, G., Garrido, J.J. & Arenillas, A. (2020). Colloids Surf. Physicochem. Eng. Asp. 604, 125248.

[2] Xing, A., Zhang, J., Bao, Z., Mei, Y., Gordin, A.S. & Sandhage, K.H. (2013). Chem. Commun. 49, 6743.

[3] Jia, H., Gao, P., Yang, J., Wang, J., Nuli, Y. & Yang, Z. (2011). Adv. Energy Mater. 1, 1036.

The authors thank Prof. José R. García, University of Oviedo, Spain, for his appreciated contribution.

The structure identification of core-shell nanoparticles could be splitted into two parts. The first one was the structure of the core. In the literature two different structures of the core can be found: ℽ-Fe [1] and α-Fe[2]. The second one was the structure of the shell. Because iron is very reactive it is always covered by the oxide shell. Different structures of the oxide shell were reported: Fe₃O₄ [3], α-Fe₂O₃ [4], ℽ-Fe₂O₃[5] or the mixture of these oxides [2]. The long-time stability of Fe-Fe_xO_y core shell nanoparticles was studied in [2] where the increase of oxide shell thickness was observed. On the other hand, it was observed that the core shell nanoparticles were complete oxidized after 26 hours [6].

In this contribution, the structure identification of Fe-Fe_xO_y core shell nanoparticles were done by combination of X-ray diffraction and Mössbauer spectroscopy. The verification of structure indentification was done by computer simulation of powder X-ray diffraction pattern. The model of nanoparticle was created, and X-ray powder diffraction pattern was simulated using the Debye formula [7]. The long-time stability of the core shell nanoparticles was studied in period of 6 years. It has been found that the structure of the samples was not changed during this 6 years period. The powder X-ray diffraction data was fitted by program MStruct [8]. The program MStruct has special tool for refining bimodal distribution of particles. This tool was used for one sample, where the diffraction lines of oxide had exceptionally long tails (see Fig. 1). These long tails were originating from the core shell structure. After modelling the core shell particle and calculating the powder X-ray diffraction pattern by different methods, the best match was obtained by using the Debye formula and then the MStruct program.

[1] Fernardez-Garcia M.P., Gorria P., Bilanco J.A., Fuestes A.B., Sevilla M. Boada R., Chaboy J., Schmool D. & Greneche J.-M. (2010). Phys Rev. B. 81, 094418. [2] Linderoth S,. Morup S. & Bentzon D. (1995). J. Mat. Sci. Soc. 30, 3142. [3] Somaskandan K., Veres T., Niewczas M. & Simard B.(2008) ,New journal of chemistry, 32, 201

[4] Tong G.-X., Yuan J.-H., Ma J., Guan J.-G., Wu W.-H., Li L.-Ch. & Qiao R.(2011), Materials Chemistry and Physics, 129, 1189

[5] Rojas T.C., Sanchesez-Lopez J. C., Greneche J.M., Conde A. & Fernandez A. (2004) Journal of materials science, 39, 4877

[6] Bodker F., Morup S. & Linderoth S (1994), Physical review letters,72,282

[7] Warren B.E.(1990). X-ray diffraction, Dover publication.

[8] Matej Z., Kadlecova A., Janecek M., Matejova L.,Dopita M., & Kuzel R., (2014), Powder Diffraction, 29, S35

This work was supported by grant CZ.02.1.01/0.0/0.0/15_003/0000485

Scrap iron pieces were collected from Burka Gibe workshop and cut into 6X3 cm pieces. Metal pieces were washedwith dil.HCl and absolute alcohol and dried. These metal pieces were polished with grade 4800 Emery paper and washed and used as electrode in an electrolytic cell. 250 ml of distilled water mixed with 10mg NaCl was used as electrolyte. Electrolysis was carried out with a current of 2amp and voltage was maintained about 20 volts for 3 hours. Dark precipitate was obtained. These precipitates were collected, air dried for a day and subjected to X-ray diffraction studies for identification of phases present. Next about 20 gm of the dark precipitate was taken in a silica crucible and heated for 3 hours at 900⁰ C. A brilliant brick red material was obtained. It was subjected to x-ray diffractional studies and quantitative phase analysis, which shows that red substance is a mixture of α-ferric oxide (86.6%), Magnetite (12.3%) and maghemite (1,1%). Many of the XRD peaks due to α-ferric oxide were found to be in the nanometer range from size strain- analysis. Further studies are going on.

The secondary molecular interactions are well known able to influence the organization behaviours and electrooptical responses of dispersed molecules. [1, 2] For dispersed phase domains of organic and inorganic components, including amorphous and crystalline phases, the mutual polarization is much less recognized. In general, the interactions among phases, specially crystallites, have not been envisaged yet as an approach of crystal engineering and capable factors to enhance the electrooptical features of phase domains.

Ferroelectric polymers are able to evolve unique polar crystalline phase below curie transition temperature via the lattice packing of all-trans conformers, which allocates most of substituted fluorine atoms on one side of molecular segments and hydrogen atoms on the other side. We found that the dielectric and piezoelectric responses of polymer ferroelectric lamellar crystals are significantly enhanced by the nearby ZnO nanorods crystals, and vice versa. The involved effects of mutual polarization cause both kinds of constituent crystals to adopt opposite polarization orientation. Besides, the extent of mutual interaction will decrease with the distance between nanorods region and PVDF-TrFE lamellae region increase, as shown on Figure 1. This is the first observation of mutual interaction among crystalline phases.

In our recent research success, we found that the stacking of ferroelectric lamellae has impact on piezoelectric and surface potential. With the growth of intact lamellae, the stacking of crystal will be better than the broken ones which is considered corresponding to the alignment of dipole moments. Therefore, the better stacking of lamellae will possess lower surface potential, however the piezoelectric response is lower, as shown on Figure 2. Besides, the mutual phases interactions have been identified between quantum dots and polymer ferroelectric crystals. With the average deposition of graphene and MoS₂ quantum dots, the piezoelectricity of dispersed ferroelectric polymer crystals has been dramatically enhanced, and graphene quantum dots are able to yield better contribution. This mutual phase interactions among ferroelectric polymer crystals and 2D material quantum dots have been explored as a helpful factor to improve the recombination issue of photocatalysts and therefore enhance the efficiency of water splitting. The involved phase evolution and growth mechanisms have been under investigation, which is expected to serve as a new direction to prepare hybrid crystalline materials able to overcome the current materials application bottlenecks.

[1] Ghosh, T., Panicker, J. S., & Nair, V. C. (2017). Self-assembled organic materials for photovoltaic application. Polymers, 9(3), 112.

[2] Liu, Y., Song, J., & Bo, Z. (2021). Designing high performance conjugated materials for photovoltaic cells with the aid of intramolecular noncovalent interactions. Chemical Communications, 57(3), 302-314.

Growth and stability of SmS-TaS₂ nanotubes studied by XAFS and DAFS methods.

It is known, that during the nanotube (NT) synthesis additional unwanted phases often occur (platelets, fullerenes, amorphic content, etc.)[1] and it is very hard or even impossible to disentangle the information about the NTs from the data achieved by macroscopic methods. The purpose of this study is to show the advantages of the DAFS (Diffraction Anomalous Fine Structure) spectroscopy technique in the analysis of NT powders containing a sufficient number of unwanted phases. This technique, based on the measurement of the diffraction peak intensity in the vicinity of the X-ray absorption edge, could bring additional spectroscopic information about the tubes in the powder mixture. Contrary to conventional XAFS (X-ray absorption Fine Structure) spectroscopy, DAFS allows to measure the XAFS-like signal from a certain phase or crystallographic site separately by choosing the proper diffraction peak [2].

NTs have several diffraction features, that distinguish them from the conventional 3D crystals and single 2D layers, that are based on the same structural units/layers (Carbon nanotubes vs Graphite, etc). Due to the lack of the out-of-plane symmetry diffraction patterns of the NTs usually doesn’t show the distinct reflections of the h0l and 0kl type, that distinguish them from the bulk particles; contrary to the single 2D layers the multilayered NTs show the reflections of 00l type due to diffraction from the basal planes of the NT [3]. These 00l and hk0 reflections can be used to get information about the NTs using the DAFS technique from NT raw powder.

In order to understand the growth and stability of SmS-TaS₂ NT a set of NT powders were synthesized by chemical vapor transport method (CVT) [2] at different temperatures (800, 825, 850, 875, 900, 925, 975, 1050 C). It was found from XRD that a small amount of Ta_1.2S₂ and Ta_1.08S₂ present in all samples, intensity of Sm₂Ta₃S₂O₈ and SmTaO₄ phases starts to grow prominently at 875 C temperature. From XRD and electron microscopy studies it was also found that the NT abundancy falls down with temperature. XAFS-like spectra derived from NT 002 and 026 reflections DAFS also (Fig. 1) shows temperature dependence: the intensity of Ta L3 ‘white’ line decrease with temperature. Such dependence of ‘white’ line intensity on NT abundancy can be explained by the difference in the interaction of SmS and TaS₂ layers in bulk SmS-TaS₂ crystals and SmS-TaS₂ NT. In the bulk SmS-TaS₂ crystals (usually defined as (SmS)_1.19TaS₂) it was found that SmS layer act as a donor of electrons for the TaS₂ part [4]. In the NT due to the curvature of the layer, the number of the SmS units is smaller than in the bulk crystals, thus SmS part donates fewer electrons. Therefore, in NT there should be more Ta 5d band vacancies in comparison to bulk, thus providing a more intense Ta L3 ‘white’ line in XANES spectra.

Figure 1. XAFS-like spectra derived from 002 reflection (left) DAFS, ‘white’ intensity derived from 002 (right-top), and 026 (right-bottom) reflections DAFS.

[1] Serra, M. et al. (2020). Appl. Mater. Today. 19, 100581.

[2] Kawaguchi, T., Fukuda, K. & Matsubara, E. (2017). J. Phys. Condens. Matter. 29, 113002.

[3] Khadiev, A. & Khalitov, Z. (2018). Acta Crystallogr. Sect. A Found. Adv. 74, 233.

[4] Wiegers, G. A., Meetsma, A., Haange, R. J. & de Boer, J. L. (1991). J. Less Common Met. 168, 347.

The Debye scattering equation, as an orientation average of summation of electromagnetic waves scattered by scattering objects, was derived by Peter Debye in 1915 [1]. The intensity scattered by isotropic ensemble of scattering objects can be expressed as

I(q) = ∑_i∑_j f_i(q)f_j(q) sin(qr_ij)/qr_ij (1)

where q = 4π sinθ / λ is the magnitude of scattering vector, 2θ is the scattering angle, λ is the wavelength of used radiation, r_ij is the distance between scatterer centres (atoms) i and j and f_i, f_j are the atomic scattering factors of atoms i and j.

Since its derivation, because of its generality, the equation was successfully used for calculation of scattered intensity from various ensembles of isotropic atomic clusters and structures. The biggest drawback, significantly restricting its use, is its computational demandingness. The evaluation of double sum is computationally time consuming since it scales as N(N-1)/2, N being the number of atoms in the cluster. Various approaches and tricks were adopted in past, as binning of inter-atomic distances, etc. to overcome this drawback and speed up the calculation.

Another approach, driven by a fast development of personal computers and graphics processing units (GPU), in past years, is the use of parallel computation for the Debye equation evaluation. This concept is described and discussed in details in [2, 3] who used the NVIDIA graphics processing units with CUDA (Compute Unified Device Architecture) for calculation of Debye equation on GPU in C or C++ languages. The parallel computing approach using GPU significantly speeds up the calculation.

Using the GPU one can calculate the Debye equation for nanomaterials, nanoclusters, nano-scaled objects, clusters violating the crystallographic symmetry or disordered materials directly without any additional structural assumptions or atomic distances histogram binning. In that case the Debye equation evaluation using modern GPU is relatively fast, however significant time consuming part of the whole process is the real space atomic cluster generation and mainly passing of the atomic cluster parameters (atomic types, coordinates, occupancies and temperature factors) into GPU.

In our work we used parts of the C++/CUDA cuDebye code [3] combined with Matlab GPU computing support for Debye equation calculation. This procedure strongly benefits from simple and flexible atomic cluster generation performed in Matlab and mainly from fast memory access and data transfer of atomic cluster parameters (even for a big clusters) to GPU for Debye equation calculation. Fast atomic cluster generation and modification in Matlab together with fast data transfer to GPU memory allows not only the intensity simulation for individual atomic clusters, but as well nanoparticle real structure fitting using the Debye equation. This procedure was successfully tested on non crystallographic nanoparticle clusters and relaxation effects modelling, and fitting of stacking faults, defects and the real structure parameters in Si, Ag, Au, Cu, Pt and Ir nanoparticles, and Fe@FeO, NaYF₄ and Ag@Ti core@shell nanoparticles.

[1] Debye, P. (1915). Ann. Phys., 46, 809. [2] Gelisio L, Azanza Ricardo CL, Leoni M, Scardi P. (2010) J Appl Cryst, 43, 647. [3] Rudolph, M., Motylenko, M., Rafaja, D., (2019). IUCrJ, Vol. 6, pp. 116-127.

A characteristic feature of quantum materials is the presence of lattice degrees of freedom manifesting themselves as local structural distortions leading to competing ground state phases and exotic behavior. More often than not, the distortions are not well expressed and/or perfectly periodic, making it difficult to identify and quantify them using traditional crystallographic techniques. We will demonstrate the advantages of total x-ray scattering and large-scale structure modeling in studying the temperature and composition evolution of lattice instabilities related to the emergence of charge density wave (CDW) and superconducting (SC) orders in archetypal Ta(Se/Te)₂ quantum materials. In particular, we will show that the low-temperature CDW phase of hexagonal 2H-TaSe₂ emerges via a gradual buildup of locally correlated clusters of Ta atoms, and not via a sudden onset of a Ta superstructure at the transition temperature [1]. We will also show the presence of a hierarchical relationship among the crystal lattice, CDW and SC orders in ternary Ta-Te-Se solid solutions, where different degrees of crystal lattice order appear to promote and maintain the competing CDW and SC orders to a different extent. The relationship may well explain the observed irregular evolution of the SC transition temperature with the relative Te to Se ratio in the solid solutions [2].

1. V. Petkov et al. Phys. Rev. B 101, 121114(R) (2020).
2. V. Petkov et al. Phys. Rev. B 103, 094101 (2021).

Modern materials science is increasingly concerned with the engineering of the periodic and aperiodic features of crystalline materials, thus making structural information on both aspects a key analytical target. In this regard, diffuse scattering from single-crystal diffraction data contains a wealth of structural information, which has been already used to unravel the local 3D structures of several inorganic and organic materials.^[1] Yet, the use of this analysis remains a long-lasting challenge in the field of one of the most researched and ubiquitous materials, metal–organic frameworks (MOFs).

In our work, we elucidated the defect structure of the renowned MOF ZIF-90^[2] by Monte Carlo based single-crystal diffuse scattering simulations (Figure 1). Our analysis showed how correlated disorder of framework components induces lattice distortions affecting the framework local symmetry and porosity. Moreover, we observed that these characteristics are influenced by the synthetic conditions and are always present in ZIF-90 crystals. While allowing a new understanding of the structure-property relationship of this MOF, our study provides a blueprint for future total-scattering studies of MOF single crystals featuring entangled substitutional and displacive disorder.

[1] T. R. Welberry, T. Weber, Crystallography Reviews 2016, 22, 2–78.

[2] W. Morris, C. J. Doonan, H. Furukawa, R. Banerjee, O. M. Yaghi, Journal of the American Chemical Society 2008, 130, 12626–12627.

There is no question that atomic pair distribution function analysis has had a profound impact on the analysis of crystalline and amorphous materials[1]. As a complement to the use of synchrotron sources for collecting PDF data, we have explored the use of home laboratory-based single crystal diffractometers to analyze both crystalline and amorphous materials. In order to generate the most useful reduced radial distribution functions, G(r), we have found it necessary to modify existing code in CrysAlis^Pro[2] and develop new code to generate G(r) data for refinement in PDFgui[3]. In this presentation we will explore the collection and analysis of total scattering data on both crystalline and amorphous materials with wavelengths readily available to home laboratory systems.

[1] Underneath the Bragg Peaks: Structural Analysis of Complex Materials, T. Egami and S. J. L. Billinge, Elsevier, Amsterdam, 2012, ISBN: 978-0-08-097133-9.

[2] Rigaku Oxford Diffraction, (2021), CrysAlisPro Software system, version 1.171.41.64, Rigaku Corporation, Wrocław, Poland.

[3] C. L. Farrow, P. Juhás, J. W. Liu, D. Bryndin, E. S. Božin, J. Bloch, Th. Proffen and S. J. L. Billinge, PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals, J. Phys.: Condens. Matter, 19, 335219 (2007)

Reverse Monte Carlo (RMC) model is a powerful tool based on supercell approach, targeting at the structure model that explains comprehensive experimental datasets. Typically, the RMCProfile package can incorporate neutron/X-ray total scattering, Bragg and extended X-ray absorption fine structure (EXAFS) data. For practical implementation, apart from theoretical pattern calculation and structure model adjustment based on metropolis algorithm, there are various effects under certain circumstances that one needs to take into account to avoid artificial effects. Here we are going to introduce several different types of correction that we recently developed and implemented, in the framework of RMCProfile, namely, 1) the correction for nano-size effect concerning total scattering modelling for nano-systems from 0D nanoparticles to 2D nanosheets [1]. 2) the implementation of arbitrary Bragg peak profile in a tabulated manner, through interacting with Topas software [2]. 3) the correction for finite instrument resolution effect going beyond the conventionally used analytical approach based on Gaussian assumption for peak shape [2]. Through such development and implementation, we hope to extend the scope of application of RMCProfile package for solving structural problems from local perspective. Typically, the implementation of resolution correction enables the modelling to an otherwise-unreachable super-large length scale, e.g., 100 Å, following the supercell approach.

Thin film structures that exhibit exotic phases and topologies have attracted the attention of diverse condensed matter communities. X-ray characterization-based investigations on such systems have been so far restricted to the study of microstructural analysis such as epitaxial match between substrate and film and of the polarization domain sizes and arrangements. Detailed investigations of the local atomic structure and the complex interplay between polarization states within the domains and the domain walls have remained elusive with X-ray diffraction. Here, we present an approach for atomic-scale structural characterization of ferroelectric single crystalline thin films based on comprehensive three-dimensional diffuse scattering data sets. The diffuse scattering will be evaluated with the three-dimensional pair distribution function (3D-ΔPDF) method¹. Specifically, we investigate superlattices of alternating ferroelectric lead titanate and dielectric strontium titanate layers with complex electrical polarization structures^2,3. This work does not only gain insights on structure-property correlations of epitaxially grown single crystalline thin films, but also lay groundwork for developing experimental and modelling tools for analyzing the local structures of thin films.

¹ Weber & Simonov 2012

² Yadav A. et al. 2016

³ A. R. Damodaran et al. 2017

in the attached file