Your research is finally out? Congratulations! But, let’s not forget that the research publication is not the end of the process, but the beginning of another one, also important: communication. Mastering communication, and all communications tools, especially social media, is now crucial to promote your research. Scientists themselves are sometimes embracing roles that were conventionally taken on by trained science communicators.

But how to exist regarding the huge flow of communication generated on social media? How to engage with new audience? How do people, outside of the scientific life, learn about science or crystallography?

The ESRF’s communication group has developed a digital strategy based on humanising science to reach new audience but also to engage people with science. This strategy aims to explain the stories behind the science carried out at the ESRF, to highlight the people behind the research projects, through digital campaigns such as “Humans of ESRF”, EBS stories or video portraits.

Social media, as the name suggests, is a useful tool for staying connected socially with one another, however more recently it has also been used to spread ideas and communicate science to a broad audience. Social media platforms such as Instagram, Twitter, Facebook and Youtube are increasingly being used to explain difficult scientific concepts in easy to understand language to a broad audience of both other scientists and other members of the public. This presentation will discuss how scientists can use social media to communicate their science, and how I have used platforms such as Instagram and Twitter to talk about crystallography and biochemistry in an accessible manner. This presentation will also dive into how scientists and science communicators have used social media in an attempted to break down the barriers between scientists and the rest of the public, and improve public perception of who scientists are and what we do.

Social media has the power to change people’s lives, from what we wear and eat, to where we go and who we socialise with. How can we leverage this influence to help inspire a new generation of scientists and crystallographers?

At the Cambridge Crystallographic Data Centre (CCDC) we are involved in several projects to demonstrate the power of structural data in fun and engaging ways on social media. Over the last year we have created games and content targeted at inspiring a new generation of scientists. This has included a wide variety of activities and social media campaigns and is often done in conjunction with people in our community.

This talk will highlight some of these efforts and explore what we have learnt along the way. We will demonstrate how we have used social media to enable people to play fun educational card games, to share instructional videos and playlists, to share educational tips (#CSDTopTipTuesday) and to encourage good data sharing practices.

We will conclude by summarising what we have learnt along the way and explore how we can better help others to spread the science of crystallography and its application as far as possible inside and outside the crystallographic community.

There is no doubt that the internet and social media has changed the way in which information is communicated and spread throughout the world today. Perhaps one of the fastest moving forms of media are memes, a small statement, image or video that is spread across platforms similarly to the game of ‘telephone’. Wikipedia defines a meme (/mi:m/MEEM) as “an idea, behaviour, or style that spreads by means of imitation from person to person within a culture – often with the aim of conveying a particular phenomenon, theme, or meaning represented by the meme.” [1] With the rise of meme groups such as “Inorganic Memes for C2v Teens” and “X-ray Crystallography May-Mays” on platforms such as Facebook, we see the spread of scientific memes and crystallographic ideas across the younger generation [2,3]. In this presentation, we will provide an overview on the use of memes to spread scientific information and their use as a tool for education and outreach for the next generation of crystallographers.

Since the turn of the century, secondary batteries have become big business. The portable electronics industry in the 1990’s was driven by the design of the Li-ion battery, and in more recent times, these batteries are underpinning the drive for electrification of vehicles to mitigate the increasingly apparent effects of climate change; thus Li-ion batteries can be described as being everywhere in everyday life.

With our reliance on portable electronics, and the growth of the electric vehicle market, it is important to not only inspire the younger generation to think of their future career in the sciences, but also allow for important concepts which relate to policy to be accessible and understandable to the wider public.

Common current outreach demonstrations for battery work make use of potato-/lemon-electrolyte batteries with a copper coin and zinc nail. Although a great demo to introduce the concept of electrochemical potentials between the metals and circuits, students often struggle to differentiate between the two types of batteries – primary (non-rechargeable) and secondary (rechargeable) and often mistakenly assume the voltage generated to originate from the potato/lemon itself.

With this in mind, we have set out to create demonstrations, which can complement primary battery demos, while showcasing operation of rechargeable batteries using the LiCoO₂ – graphite as a basis of the set-up. The talk will highlight our work from the past year through a variety of demonstrations, including our battery jenga¹ set-up and the Royal Society of Chemistry IYPT2019 funded Lithium Shuffle Project battery operation videos². The talk will also touch on outreach funding – the highs and lows, and how the group has continued their engagement work during the difficult period of COVID19.

The Italian Young Crystallographers (trad. Giovani Cristallografi Italiani aka GCI) group was formally established in 2019 driven by the need of having a common place for students and young researchers to share their experiences and develop a common sense of affiliation to the main national association.

However, the possibility to meet each other at conferences and congresses are rather modest even without the well-known pandemic constraints, so, we decided to use social media to share information among the community on a regular basis. The social media platforms soon became a virtual place where the young generation of crystallographers are informed of job vacancies around the world, promote their latest research and enrich their crystallographic knowledge.

As a consequence, the number of younger scientists associated increased significantly in the last two years and the GCI, fully supported by the national crystallographic association, plays a central role in all the scientific activities organized locally and at the national level.

I here report the strategies used to develop the social media platforms and the initiative promoted by GCI to engage young researchers in crystallography.

As part of a continuing project, the challenging room-temperature crystal structures of eight commercial pharmaceutical APIs have been solved by Monte Carlo simulated annealing techniques using synchrotron X-ray powder diffraction data (11-BM at APS), and optimized using density functional techniques. Tofacitinib dihydrogen citrate (Xeljanz®), (C15H21N6O)(H2C6H5O7), crystallizes in P212121 with a = 5.91113(1), b = 12.93131(3), c = 30.43499(7) Å, V = 2326.411(6) Å3, and Z = 4. All of the “interesting” hydrogn atoms could be located by analysis of potential hydrogen bonding patterns. Eltrombopag olamine Form I (Promacta®), (C2H8NO)2(C25H20N4O4) crystallizes in P21/n with a = 17.65884(13), b = 7.55980(2), c = 22.02908(16) Å, β = 105.8749(4)̊, V = 2828.665(11) Å3, and Z = 4. The initial structure solution reversed the orientation of one of the cations. Levocetirizine hydrochloride Form I (Zyzal), C21H27ClN2O3Cl, apparently crystallizes in P21/n (even though it is a chiral molecule and exhibits weak second-harmonic generation) with a = 24.1318(21), b = 7.07606(9), c = 13.5205(7), β = 97.9803(4)̊, V = 2286.38(12) Å3, and Z = 4. Edoxaban tosylate monohydrate Form I (Lixiana®), (C24H31ClN7O4S)(C7H7O3S)(H2O), crystallizes in P21 with a = 7.55097(2), b = 7.09010(2), c = 32.08420(21) Å, β = 96.6720(3)̊, V = 1744.348(6) Å3, and Z = 2. Tezacaftor Form A (Symdeko), C26H27F3N2O6, crystallizes in C2 with a = 21.05142(2), b = 6.60851(2), c = 17.76032(5) Å, β = 95.8255(2)̊, V = 2458.027(7) Å3, and Z = 4. Pomalidomide Form I (Pomalyst), C13H11N3O4, crystallizes in P-1 with a = 7.04742(9), b = 7.89103(27), c = 11.3106(6) Å, α = 73.2499(13), β = 80.9198(9), γ = 88.5969(6)̊, V = 594.618(8) Å3, and Z = 2. Palbociclib isethionate Form B (Ibrance®), (C24H30N7O2)(C2H5O4S), crystallizes in P-1 with a = 8.71337(4), b = 9.32120(6), c = 17.73722(20) Å, α = 80.0258(5), β = 82.3581(3), γ = 76.1560(2)̊, V = 1371.284(5) Å3, and Z = 2. Osimertinib mesylate Form B (Tagrisso), (C28H34N7O2)(CH3O3S) crystallizes in P-1 with a = 11.4291(3), b = 11.7223(4), c = 13.3221(4), α = 69.0246(8), β = 74.5906(7), γ = 66.4001(7)̊, V = 1511.466(13) Å3, and Z = 2. Other new structures may be discussed as they become available.

Structure determination of organic materials directly from powder X-ray diffraction (XRD) data [1,2] is now carried out extensively by researchers in both academia and industry. Most research in this field uses the direct-space strategy for structure solution [3,4] followed by Rietveld refinement. Although the structure determination process is generally carried out solely using powder XRD data, significant advantages may be gained by augmenting the process of structure determination from powder XRD data by utilizing information obtained from other experimental and computational techniques. Such multi-technique approaches are particularly advantageous in tackling complex and challenging structure determination problems, both by providing independent information that may be used directly to facilitate the structure determination process and by allowing robust validation of the final structure obtained in the Rietveld refinement. The lecture will focus on the use of solid-state NMR spectroscopy and periodic DFT-D calculations to augment the process of structure determination of organic materials from powder XRD data [5-11]. The lecture will present several case studies from recent research, including several examples of polymorphic systems and pharmaceutical materials. Recent examples exploiting the complementary advantages of 3D electron diffraction data and powder XRD data within the structure determination process will also be presented.

[1] Harris, K. D. M., Tremayne, M. & Kariuki, B. M. (2001) Angew. Chemie Int. Ed. 40, 1626.

[2] Harris, K. D. M. (2012) Top. Curr. Chem. 315, 133.

[3] Harris, K. D. M., Tremayne, M., Lightfoot, P. & Bruce, P. G. (1994) J. Am. Chem. Soc. 116, 3543.

[4] Kariuki, B. M., Serrano-González, H., Johnston, R. L. & Harris, K. D. M. (1997) Chem. Phys. Lett. 280, 189.

[5] Dudenko, D. V., Williams, P. A., Hughes, C. E., Antzutkin, O. N., Velaga, S. P., Brown, S. P. & Harris, K. D. M. (2013) J. Phys. Chem. C 117, 12258.

[6] Williams, P. A., Hughes, C. E. & Harris, K. D. M. (2015) Angew. Chemie Int. Ed. 54, 3973.

[7] Watts, A. E., Maruyoshi, K., Hughes, C. E., Brown, S. P. & Harris, K. D. M. (2016) Cryst. Growth Des. 16, 1798.

[8] Hughes, C. E., Reddy, G. N. M., Masiero, S., Brown, S. P., Williams, P. A. & Harris, K. D. M. (2017) Chem. Sci. 8, 3971.

[9] Hughes, C. E., Boughdiri, I., Bouakkaz, C., Williams, P. A. & Harris, K. D. M. (2018) Cryst. Growth Des. 18, 42.

[10] Al Rahal, O., Hughes, C. E., Williams, P. A., Logsdail, A. J., Diskin-Posner, Y. & Harris, K. D. M. (2019) Angew. Chemie Int. Ed. 58, 18788.

[11] Al Rahal, O., Williams, P. A., Hughes, C. E., Kariuki, B. M. & Harris, K. D. M. (2021) Cryst. Growth Des. 21, 2498.

Crystal engineering has emerged as an important field of solid-state chemistry, developing tools to deliberately design functional organic solids. A particularly exciting aspect of crystal engineering is the tuneability of physicochemical properties of organic solids such as solubility, thermal stability, bioavailability etc. without altering the underlying molecular structure(s) – a concept of high relevance for pharmaceutical industry.^[1] Altering physisochemical properties can be achieved by relying on different solid forms, such as polymorphs, cocrystals, and salts.^[2] The latter two are multicomponent systems that, in organic solids, are essentially distinguished by the position of a proton within the crystal structure. While different chemical systems can appear in different forms, proton transfer has rarely been observed for multicomponent systems with identical stoichiometric composition.^[3]

In this contribution, we present an extremely rare case of polymorphism between a metastable molecular (cocrystal) and ionic (salt) form of a two-component system based on nicotinamide and a dicarboxylic acid, induced by supramolecular tautomerism. In specific, we show the polymorphic transition from a metastable cocrystal to a salt, monitored using time-resolved powder X-ray diffraction (PXRD) and solid-state nuclear magnetic resonance spectroscopy. Both formerly unknown structures of were solved ab initio from PXRD data and further analyzed using spectroscopic methods, as well as density functional theory calculations.

Figure 1: Monitoring the polymorphic transition from metastable cocrystal to salt using (a) PXRD and (b) ¹⁵N ssNMR spectroscopy.

[1] Almarsson, O. & Zaworotko, M, J. (2004). Chem. Commun., 17, 1889-1896. [2] Aitipamula, S. et al. (2014), Cryst. Growth Des., 12, 2147−2152 [3] Bernasconi, D., Bordignon, S., Rossi, F., Priola, E., Nervi, C., Gobetto, R., Voinovich, D., Hasa, D., Tuan Duong, N., Nishiyama, Y., Chierotti, M. R., (2020). Cryst. Growth Des., 20, 906-915.

In the pharmaceutical crystal, hydration/dehydration phase transitions are often observed phenomena during manufacturing or storage. They lead the substantial crystal structure change, so they are critical for the important physicochemical properties that depend on the crystal structure, such as stability, solubility, and bioavailability. However, after dehydration, single-crystal integrity tends to degrade, resulting in powdery crystals. We have successfully revealed solid-state structural rearrangements using ab initio Structure Determination from Powder X-ray Diffraction data (SDPD) technique [1-4]. Interestingly, some crystals show "isomorphic desolvation," in which the XRD pattern does not change significantly after dehydration, meaning the initial molecular arrangement is well preserved. We can reveal an isomorphic desolvation mechanism by comparing the crystal structures from powdery crystals in the hydration/dehydration phase transitions, which can be achieved using the SDPS technique.

Carbazochrome sodium sulfonate trihydrate, a hemostatic agent, undergoes stepwise dehydration by humidity control or heating. The hydration number decreased from 3 to 2.5, 2, 1, and anhydrous form I under dry condition, and it showed isomorphic desolvation (Fig. 1). Their crystal structures were analysed by SDPD technique to show the API molecules are linked through Na cations to form polymeric structure, and the molecular arrangements were very similar. It is noteworthy that the first dehydration did not occur at non-coordinated crystalline water C, but water molecules A and B which coordinated to Na cation were dehydrated in sequence. This removal order was explained by the crystal structures' stability after each dehydration, calculated using CASTEP quantum mechanics calculations. Even after dehydration, the molecular arrangements were almost kept by adjusting the molecular positions slightly. After removing crystalline water C, the crystallinity degraded significantly, indicating the molecule C is essential for stabilizing the whole crystal structure. Thus, the mechanism of the stepwise dehydration behaviour, and isomorphic desolvation were revealed by SDPD technique.

Figure 1. Chemical diagram and molecular arrangement of trihydrate, dihydrate, and monohydrate phases of Carbazochrome sodium sulfonate.

[1] Fujii, K., et al. (2010) J. Phys. Chem. C 114, 580.

[2] Fujii, K., Uekusa H., Itoda N., Yonemochi E. & Terada K. (2012) Cryst. Growth Des. 12, 6165.

[3] Fujii, K., Aoki, M. & Uekusa, H. (2013) Cryst. Growth Des. 13, 2060.

[4] Putra, O. D., Yonemochi, E., Pettersen A. & Uekusa H. (2020) CrystEngComm 22, 7272.

Keywords: Structure Determination from Powder X-ray Diffraction data; dehydration; crystal structure, pharmaceutics; quantum mechanics

Part of this work was supported by JSPS KAKENHI Grant Number JP18H04504 and 20H04661 (HU).

Trichlormethiazide is a thiazide derivative, an important group of diuretic drugs, which is used in the treatment of hypertension. The Cambridge Structural Database (CSD) contains only one report (KIKCUD) associated with this pharmaceutical [1], corresponding to the orthorhombic form of anhydrous S-Trichlormethiazide. The PDF-4/Organics database contains two entries. One is the calculated pattern of the CSD entry (PDF 02-094-5865) and the other is an experimental unindexed pattern (PDF 00-039-1828). In this contribution the structure of racemic Trichlormethiazide was determined from laboratory X-ray powder diffraction data. This material was also characterized by FT-IR, TGA and DSC. The structure was determined with DASH [2] and refined by the Rietveld method with TOPAS-Academic [3]. The final unit-cell parameters are a = 8.4389(6), b = 8.8929(7), c = 9.7293(8) Å, α = 91.315(3)°, β = 106.113(2)°, γ = 97.1580(17)°, V = 694.73(9) ų, Z = 2. The refinement converged to R_p = 0.0512, R_wp = 0.0694, and GoF = 2.704. In the crystal structure, the molecules form chains along the a-axis connected by cyclic N-H···N and N-H···Cl hydrogen bonds. The chains are connected by additional cyclic N-H···Cl hydrogen bonds to form layers almost parallel to the ab plane. The fingerprint plots and energy frameworks diagrams of S and racemic forms clearly show the different intermolecular interactions and their topologies. A detailed discussion will be present in this work.

Ab initio structure determination from Powder X-ray Diffraction (PXRD) data is continuously demonstrating its merit thanks to advances in modern phasing algorithms, computing power and X-ray instrumentation. As the technique has long passed the question “can it be done”, there is another question to answer: “how far can it be pushed”. In this respect, this presentation has two aims: (i) to show methodologies that allow for solving of difficult structures of organic molecules and (ii) to highlight the level of accuracy that can be obtained from PXRD data.

This presentation is focused on structure determination of crystals that feature large molecules, disorder, or radiation-induced changes. The first part of the presentation outlines a phasing methodology that can result in an interpretable structural model. The methodology relies on the phasing process in the charge-flipping program [2] Superflip [3] by introducing a partial or incorrect structure obtained by a direct-space algorithm FOX [4]. The second part of the presentation will address structure completion and refinement, and highlight examples of how high quality data can be used for restraint-free Rietveld refinement, modeling disorder from difference Fourier map, and for obtaining insights in bond order disambiguation.

While the majority of shown examples rely on PXRD data collected at synchrotron sources, the potential of data collected in a laboratory diffractometer will also be discussed.

[1] Šišak Jung, D. et al. (2014). J. Appl. Cryst. 47, 1569-74
[2] Oszlanyi, G., Sütő, A. (2004). Acta Cryst. A60, 134-141
[3] Palatinus, L., Chapuis, G. (2007). J. Appl. Cryst. 40, 786-790
[4] Favre-Nicolin, V., Černý, R. (2004). Z. Kristallogr. 219(12), 847-856.

The idea for ptychography dates back to 1969, but its realization as a practical imaging method awaited the development of iterative phase retrieval algorithms. By now, it is firmly established for nanoscale studies of materials using X rays, both in transmission mode and also using Bragg diffraction. While focusing optics greatly aid its implementation, the spatial resolution is determined not by optics but by the finest length scales from which one can measure elastic scattering. On the experimental side, the hundredfold increases in quasi-time-continuous coherent flux provided by diffraction-limited storage rings will dramatically advance what ptychography can do. On the computational side, the application of nonlinear optimization approaches has allowed one to compensate for many experimental limitations, including errors in nanopositioning as well as partial coherence, and allow one to re-think how one might acquire ptychographic data. Thus far, x-ray ptychography has been applied to millimeter-size samples in 2D, and roughly 10 micrometer size samples in 3D. How far might that go? Can one combine the advantages of X rays of high penetration power and low multiple scattering to image even larger samples? Can one carry out nanoscale imaging of cubic centimeter volumes? I outline some of the opportunities this might provide, and some of the challenges in achieving this.

Recent developments in 4th generation light sources and high-speed detectors are leading to rapid growth in data rates and data volumes, increasing the demand for automated data collection, handling/reduction/storage, and analysis processes. In combination with limited in-person access to experimental setups in times of the pandemic, portable and user-friendly tools for remote access as well as improved workflows are critical for enabling scientists from various disciplines to leverage ptychographic imaging to answer scientific questions.

With the growing popularity of ptychography, a broad range of data formats, acquisition schemes, and algorithms has been developed over the years, e.g. [1-3]. Whereas this variety has been advantageous to tackle different real-world deviations from the ideal ptychographic model such as partial incoherence [4], positioning errors [5], broad-bandwidth radiation [6], or multi-scattering [7], it also complicates the comparability and reproducibility of results. With ptychography being established as an everyday workhorse technique at many instruments around the world, it is important to find common ground and establish standards to support reliable algorithm and collaborative software development addressing the big data challenges of today and the future.

In this presentation, I will cover recent cross-facility efforts [8] to develop and promote data standards for ptychography. Furthermore, I will give an overview of ongoing software development at the Advanced Light Source in collaboration with the other DOE light sources for building data acquisition and analysis tools leveraging existing python packages with an outlook for future progress in terms of remote access and workflows.

[1] Enders B., & Thibault P., (2016). Proc Math Phys Eng Sci. 472(2196) 20160640.

[2] Wakonig K., Stadler H.-C., Odstrčil M., Tsai E. H. R., Diaz A.,Holler M.,Usov I., Raabe J., Menzel A., & Guizar-Sicairos M. (2020). Journal of Applied Crystallography, 53(2) 574-586

[3] Favre-Nicolin V., Girard G., Leake S., Carnis J., Chushkin Y., Kieffer J, Paleo P. & Richard M.-I. (2020). J. Appl. Cryst. 53, 1404-1413

[4] Thibault P. & Menzel A. (2013). Nature 494, pages 68–71

[5] Maiden A.M., Humphry M.J., Sarahan M.C., Kraus B. & Rodenburg J.M., (2012). Ultramicroscopy, 120, 64-72

[6] Enders B., Dierolf M., Cloetens P., Stockmar M., Pfeiffer F. & Thibault P., (2014). Appl. Phys. Lett. 104, 171104

[7] M Kahnt, Grote L, Brückner B., Seyrich M., Wittwer F., Koziej D. & Schroer C. G., (2021). Sci Rep 11, 1500

[8] Data Solution Task Force Pilot https://www.bnl.gov/newsroom/news.php?a=216902

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under the Data Solution Task Force Pilot.

The work was partially funded through the Center for Advanced Mathematics for Energy Research Applications (CAMERA), which is jointly funded by the Advanced Scientific Computing Research (ASCR) and Basic Energy Sciences (BES) within the Department of Energy’s Office of Science, under Contract No. DE-AC02-05CH11231.

This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory, operated under Contract No. DE-AC02-05CH11231.

This work was supported by the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by ANL under contract No. DE-AC02-06CH11357.

This research used resources of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Cement manufacturing is responsible for ~7% of the anthropogenic CO₂ emissions and hence, decreasing the CO₂ footprint, in a sustainable, safe, and cost-effective way, is a top priority. It is also key to develop more durable binders as the estimated world concrete stock is 315 Gt which currently results in ~0.3 Gt/yr of concrete demolition waste (CDW). Moreover, models under development predict a skyrocketing increase of CDW to 20–40 Gt/yr by 2100. This amount could not be easily reprocessed as aggregates for new concretes as such volumes would be more than two times the predicted need. Furthermore, concretes have very complex hierarchical microstructures. The largest components are coarse aggregates with dimensions bigger than a few centimetres and the smallest ones are amorphous components and the calcium silicate hydrate gel with nanoparticle sizes smaller than a few nanometres. To fully understand the properties of current and new cement binders and to optimize their performances, a sound description of their spatially-resolved contents is compulsory. However, there is not a tomographic technique that can cover the spatial range of heterogeneity and features of concretes and mortars. This can only be attained within a multitechnique approach overlapping the spatial scales in order to build an accurate picture of the different microstructural features. Here, we have employed far-field and near-field synchrotron X-ray ptychographic nanotomographies to gain a deeper insight into the submicrometer microstructures of Portland cement binders. With these techniques, the available fields of view range from 40 to 300 mm with a true spatial resolution (not voxel sizes) evolving between ~50 nm to ~300 nm. It is explicitly acknowledged here that other techniques like X-ray synchrotron microtomography are necessary to develop the whole picture accessing to larger fields of view (millimetres and even centimetres) albeit with poorer spatial resolution and without the quantitativeness in the reconstructed electron densities.

After framing the problems which are being tackled, we plan to present here our recent results using X-ray ptychographic nanotomography. We will start introducing the outputs obtained using far-field ptychographic nanotomography to determine phase assemblages and mass densities of amorphous components [1,2]. Then, we will move to cover the secondary porosity induced by cement conversion with temperature [3]. Finally, we will present our ongoing work with near-field ptychographic nanotomography in Portland and Belite cements with a larger field of view, capillaries from 200 to 300 mm of diameter. Between other features, Hadley grains (hollow-shells hydrated particles) have been imaged in 3D and their properties are being statistically extracted, see Figure 1. Further details will be discussed and the comparison between far-field and near-field nanotomographies will be carried out.

[1] Cuesta, A., et al. (2017) Chemistry and Mass Density of Aluminum Hydroxide Gel in Eco-Cements by Ptychographic X‑ray Computed Tomography. J. Phys. Chem. C, 121, 3044−3054.

[2] Cuesta, A., et al. (2019) Quantitative disentanglement of nanocrystalline phases in cement pastes by synchrotron ptychographic X-ray tomography. IUCrJ, 6, 473–491.

[3] Shirani, S., et al. (2020) Calcium aluminate cement conversion analysed by ptychographic nanotomography. Cem. Con. Res. 137, 106201.

Wiring diagrams of neural circuits are of central importance in delineating mechanisms of computation in the brain (1). Hereby, the individual parts of neurons - axons, dendrites and synapses - need to be densely identified in 3-dimensional volumes of neuronal tissue. This is typically achieved by volume electron microscopy (2), which requires ultrathin physical sectioning or ablation, using high precision slicing techniques or ion beams, either before or during the image acquisition process (3-6). Here, we demonstrate that cryogenic X-ray ptychographic tomography (7-9), a coherent diffractive X-ray imaging technique, can acquire 3-dimensional images of metal-stained mouse neuronal tissue with sufficient resolution to densely resolve axon bundles, boutons, dendrites and synapses without physical sectioning. We show that the tissue volume can be subsequently imaged in 3D using high-resolution, focussed ion beam-scanning electron microscopy (FIB-SEM). This suggests that metal-stained neuronal tissue can be highly radiation-stable. Using FIB-SEM as ground truth, we could show that X-ray ptychography reliably resolves 60% of the synaptic contacts in the mouse olfactory bulb external plexiform layer with an 80% precision. Ongoing improvements in synchrotron, X-ray and detector technologies (8, 10, 11) as well as further optimization of sample preparation and staining procedures (12, 13) could lead to substantial improvements in acquisition speed. Combined with laminography (14) and nano-holotomography (15, 16) it could allow for non-destructive x-ray imaging of synapses and neural circuits in increasingly larger volumes.

Catalysts are ubiquitous materials that play a major role in many areas of economy and everyday life. The development and study of catalysts is important for progress in areas such as environment, energy, and fuels, with the main goal being to improve the performance and efficiency of catalysts, especially at the industrial scale. Therefore, a thorough analysis is crucial to understand the relation between structure and performance, the deactivation process and the reasons for the loss of efficiency over the lifetime. This analysis is challenging, because technical catalysts are complex multicomponent bodies, ranging from dozens of μm to several cm, consisting of active phases, supports and additives in shaped forms suitable for their application. One of the most important conversion processes in petroleum refineries is Fluid Catalytic Cracking (FCC) in which heavy hydrocarbon fractions of crude oil are converted into valuable products such as olefins and aromatics [1]. For this process, FCC particles of 50 - 100 µm diameter are used in an up-flow reactor, where they move up, whereas the feed flows downward. During the short contact time, catalyst and feed can react. During this reaction the catalyst is partially deactivated by coke formed during the cracking and a subsequent regeneration cycle is required [2]. Thus, the characterization of the microstructure at different length scales with a spatial resolution at the nanometer length scale and a large field of view is necessary, but also the investigation of the location and chemical state of the active metallic sites in the structure.

The imaging of a large field of view with a resolution of ~ 30 - 100 nm is possible with ptychography, even for low absorbing samples. To get spatial resolved spectral information, spectro-ptychography can be used, where the measurements are repeated at different energies, including the absorption edge of a specific element. This method has already been applied for the nanoscale chemical imaging and structural analysis of a heterogeneous catalyst [3].

We investigated a FCC catalyst containing 10 wt.% Mn₂O₃ at different lifetimes by means of spectro-ptychography. Ptychographic scans are repeated at 40 different energies around the Mn K-edge. We show here the results of the experiment carried out at the beamline ID16B at ESRF, where this method has never been used before. The absorption is weak due to the low concentration of Mn and the small thickness of the samples, and hence we work with the phase contrast images. The phase contrast can be associated with the anomalous scattering factor f’, which is energy dependent in the proximity of absorption edges. The f’ spectra can be extracted by comparing the reconstructed phase contrast images recorded at different energies. The work includes the preparation of the instrumentation, the development of the algorithms for the data preparation and the python programs for the spectral analysis. We show the methodological developments necessary for the extraction of the information from the obtained measurements, starting from the phase retrieval and normalization of the phase images, to the alignment of the images of different energies, to the extraction of the f’ spectra and the search for the Mn signature in the sample.

[1] W. Letzsch,Handbook of Petroleum Processing, Springer Int. Publishing, Cham 2015, 216-316.

[2] A. Corma, et al., Catalysis Science & Technology 2017, 7, 12.

[3] M. Hirose, et al., Angew. Chem. Int. Ed. 2017, 56, 1-6.

Three-dimensional X-ray microscopy by ptychographic tomography is usually per formed by separating the steps of acquiring two-dimensional ptychographic reconstructed projection images at different projection angles and afterwards performing the three-dimensional tomographic reconstruction. Recently it has been suggested that those two separate steps can be coupled / joined together, allowing for the sharing of information between angular views during the ptychographic reconstruction step [1, 2, 3]. We performed such a coupled X-ray ptychographic tomography reconstruction for the first time on an experimental dataset, improving the achieved resolution in the process [4]. Furthermore we validated the predicted relaxation of the overlap criterion between adjacent scan positions in the tomographic plane by successively leaving out columns of recorded diffraction patterns and achieving robust reconstructions even beyond the point of no
overlap between neighboring scan points.

References:

[1] D. Gürsoy, “Direct coupling of tomography and ptychography,” Opt. Lett., vol. 42, pp. 3169–3172, Aug 2017.
[2] T. Ramos, B. E. Grønager, M. S. Andersen, and J. W. Andreasen, “Direct three-dimensional tomographic reconstruction and phase retrieval of far-field coherent diffraction patterns,” Phys. Rev. A, vol. 99, p. 023801, Feb 2019.
[3] S. Aslan, V. Nikitin, D. J. Ching, T. Bicer, S. Leyffer, and D. Gürsoy, “Joint ptycho-tomography reconstruction through alternating direction method of multipliers,” Opt. Express, vol. 27, pp. 9128–9143, Mar 2019.
[4] M. Kahnt, J. Becher, D. Brückner, Y. Fam, T. Sheppard, T. Weissenberger, F. Wittwer, J.-D. Grunwaldt, W. Schwieger, and C. G. Schroer, “Coupled ptychography and tomography algorithm improves reconstruction of experimental data,” Optica, vol. 6, pp. 1282–1289, Oct 2019.

Water plays a critical role in many steps of the pharmaceutical development as this small molecule has the ability to interact with compounds in numerous ways and may therefore significantly affect manufacturing processes and finally the quality of (pharmaceutical) products. The formation of a molecular compound (hydrate), where water becomes a part of the crystal lattice, is mostly accompanied with a significant change in the solid-state properties, and therefore this type of interaction must be seen as critical [1]. Hydrate formation itself is a widespread phenomenon and is known to occur for at least one third of drug molecules [2,3], and this trend is increasing significantly for new drug substances. Nevertheless, we are still not able to predict hydrates, their stability and dehydration mechanisms based on the molecular diagram only.

This talk will emphasise on the efforts that are sometimes required to identify solid forms of complex hydrate forming systems. Examples from our research will be used to illustrate how the combination of a variety of experimental techniques, covering temperature- and moisture-dependent stability, and computational modelling allows to generate sufficient kinetic, thermodynamic and structural information to understand hydrate formation and its impacts on relevant physicochemical properties.

The solid form landscape of brucine sulphate was elucidated, resulting in three hydrate forms and amorphous brucine sulphate. HyA was produced from water and the other two by dehydration starting from HyA. Removal of the essential water molecules stabilising the hydrate structures causes a collapse to the amorphous state [4]. Eight hydrate forms were verified for the related compound, strychnine sulphate. Three of the hydrates were found to be stable at ambient conditions. The other five hydrates are only observable at low(est) relative humidity (RH) levels at room temperature. Some of the hydrates can only exist within a very narrow RH range and are therefore regarded as intermediate phases. The specific moisture and temperature conditions of none of the applied drying conditions yielded a crystalline water-free form, highlighting the essential role of water molecules for the formation and stability of crystalline strychnine sulphate [5].

Despite their structural similarity, marked differences in the formation of solid forms are seen for brucine and strychnine. One anhydrous form and 1,4-dioxane solvates were crystallized for strychnine, whereas two non-solvated polymorphs, four hydrates, an isostructural dehydrate, twelve solvates and two hetero-solvates are known to exist for brucine [6-8]. One of the brucine hydrates shows a non-stoichiometric (de)hydration behaviour, one collapses to an amorphous phase, and the third one to the polymorph which is stable at room temperature. Interestingly, each of the three hydrates may become the most stable form depending on temperature and water activity.

To conclude, this study demonstrates the importance of applying complimentary analytical techniques and appropriate approaches for understanding the stability ranges and transition behaviour between the solid forms of compounds with multiple hydrates.

[1] Khankari, R. K. & Grant, D. J. W. (1995). Thermochim. Acta, 248, 61.

[2] Stahly, G. P. (2007). Cryst. Growth Des, 7, 1007.

[3] Reutzel-Edens, S. M., Braun D. E. & Newman A. W. (2019). Polymorphism in the Pharmaceutical Industry: Solid Form and Drug Development, edited by R. Hilfiker & M. Von Raumer: Wiley-VCH, pp. 159-188.

[4] Braun, D. E. (2020). CrystEngComm, 22, 7204.

[5] Braun, D. E., Gelbrich, T., Kahlenberg, V. & Griesser, U. J. (2020). Cryst. Growth Des., 20, 6069.

[6] Braun, D. E. and Griesser, U. J. (2016). Cryst. Growth Des., 16, 6405.

[7] Braun, D. E. and Griesser, U. J. (2016). Cryst. Growth Des., 16, 6111.

[8] Watabe, T., Kobayashi, K., Hisaki, I., Tohnai, N. & Miyata, M.Bull. (2007). Chem. Soc. Jpn., 80, 464.

We have recently studied a diarylamine compound, tolfenamic acid (TFA), and examined its solution chemistry, crystallization kinetics, and molecular interactions. The polymorphic system typically crystalizes as From I or Form II, or both concurrently, with Form I being the most stable at room temperature. Both polymorphs are composed of hydrogen-bonded, carboxyl homodimers as the supramolecular synthon in their respective crystal structures. One interesting kinetic phenomenon that we experimentally discovered was an intermediate or transitional retraction of the mass composition of Form I in crystallized samples over the course of concomitant crystallization. The composition retraction bears two characteristic attributes, the retraction depth and the onset fraction. The former quantifies the maximal extent to which the Form I composition retracts prior to elevation, whereas the later attribute characterizes the initially measured Form I composition. Conversely, during solvent-mediated phase transformation, the mass composition of Form I monotonically increases and only Form II nucleates initially. We further learned through population balance simulations that this characteristically kinetic phenomenon is a sufficient condition indictor of concomitant crystallization of polymorphic systems. Interestingly, when experimental observation is made at a later time after the kinetic retraction, it seems unlikely to kinetically differentiate the two crystallization pathways.

In recent years, considerable investment has been made towards advancing pharmaceutical development and manufacturing through Digital Design approaches.¹ Industrial scientists are moving away from time and resource intensive screening techniques to more rapid in silico methods to inform key decisions throughout the drug manufacturing process.

The links between solid form and structural properties are well developed,² but our understanding of the relationship between particle and surface properties and downstream manufacturability of an Active Pharmaceutical Ingredient (API) are considerably less established. By providing new methods for visualising and describing these key attributes, we can gain a deeper insight into properties that contribute to the way particles flow or how they form tablets under compression.

Since describing these approaches and their application to the drug lamotrigine,³ we have continued to develop and refine the way that we can describe a particle and its properties. This presentation will discuss those advances and the challenges that lie ahead.

References

1. www.addopt.org

2. P.T.A Galek et al., CrystEngComm 2012, 14, 2391–2403

3. M.J. Bryant et al., Cryst. Growth Des. 2019, 19, 9, 5258–5266

Pharmaceutical industries have witnessed an increasing trend towards poor aqueous solubility and according to a report 75% of the marketed drugs belong to BCS class II or IV. Efforts to improve aqueous solubility by modifying the chemical structures are carried out during lead optimization in early drug discovery stage while trying to maintain desired potency and ADME properties. However, experimental aqueous solubility assays available during lead optimization are prone to overestimate solubility to a variable extent. This overprediction of aqueous solubility can result in overly optimistic view of developability with negative implications for compounds differentiation and candidate selection for development. On the other hand, failure to improve aqueous solubility could lead to inadequate evaluation of safety and efficacy profile of candidates and resource intensive formulation approaches. With the advancement of computations as well as due to immense pressure to shorten development timelines, in-silico approaches to predict aqueous thermodynamic solubility are of greater importance. In this presentation a physics-based ensemble modeling approach consisting of high-fidelity cloud-based crystal structure prediction (CSP) methodology optimized for computational cost and a novel free energy perturbation (FEP+) workflow is discussed to predict aqueous thermodynamic crystalline solubility of chemically structurally related compounds during lead optimization stage using just the 2-D structure as an input.

The various aspects of drug design or catalysis is compartmentalized within defined research fields, i.e. bioactivity testing versus pure synthetic chemistry; homogeneous versus heterogeneous catalysis. These are independent and often non-interactive specialities which have developed along parallel pathways with a common objective. The world economic drive towards the 4^th industrial revolution captures the idea of the confluence of new technologies and their cumulative impact on our world. Hence the ability to merge, bridge and remove boundaries will result in the establishment of interoperable research.

Drug design, particularly the development of target specific radiopharmaceuticals which involves the selective receptor binding of a radioactive organometallic complex to a possible disease site involves multiple facets. Simple manipulation of the ligand system bound to the metal centre can significantly alter parameters such as steric and electronic character, chirality, stability, biological and hydro/lipophilicity properties. Our organometallic research utilising the group 7 transition metal triad of manganese, technetium and rhenium for nuclear medical imaging and therapeutic agents, includes the interactions with proteins using protein crystallography. This provides valuable structural information in a similar vein to fragment based drug discovery (FBDD). The domain of chemical versus macromolecular crystallography has resulted in multiple discipline variations, such as incompatible software, data formatting and terminology. A key challenge which hinders research advancement is the lack of interoperability between chemical and biological crystallographic data.

This perspective will highlight the opportunities of harvesting both small molecule and macromolecular structural data, the joint usage of the CSD and PDB databases, as well as the advantages of software which can convert organometallic small molecule structural data for use in protein refinement software. This multidiscipline approach to radiopharmaceutical development will include kinetic reactivity studies highlighting how subtle structural changes can significantly affect chemical reactivity and hence the protein coordination in macromolecular structures. Trends similarly witnessed in catalysis research.

Multiple scattering in 3D electron diffraction (3D ED) experiments is responsible for deviations of diffracted intensities from intensities expected from kinematical diffraction theory [1]. Though this is usually considered a disturbing factor in routine structure determinations, these deviations also contain valuable information on the absolute structure [2]. Analysing 3D ED measurements from different laboratories around the world, we demonstrate that the absolute structure of single submicrometric crystals can be reliably and easily determined in a routine way if dynamical diffraction effects are incorporated in the refinement of the structure model.

We investigated and reinvestigated data sets of non-centrosymmetric samples recorded with beam-precession (precession-assisted 3D ED) and with continuous-rotation 3D ED (IEDT, MicroED, cRED) to determine the absolute structure, which directly determines the absolute configuration of chiral molecules in the unit cell. Dynamical effects are very sensitive to the absolute structure due to the interference of multiple beams contributing to each reflection [3]. In comparison to X-ray diffraction-based methods, the requirements for a successful determination of the absolute structure are strongly reduced. We demonstrate that with a completeness as low as 25% (Figure 1), a limited resolution d_min > 1 Šand only a preliminary structure model the correct chirality can still be identified. The low requirements also allow significantly reducing the number of refinement parameters so that the computationally demanding calculations applying dynamical diffraction theory are only a matter of minutes even for unit cells with a volume of several thousand ų. The determination is based on a simple comparison of residual factors (R_obs and wR_all) of the refined, inversion-related models (Figure 1). With this approach, the routine determination of the chirality of molecules in submicrometric crystals is ready to be implemented in any laboratory with access to 3D electron diffraction measurements. Considering ongoing developments, improvements and increasing level of automatization of data acquisition and analysis [1], we believe that especially the pharmaceutical industry will strongly benefit from the presented approach.

[1] Gemmi, M., Mugnaioli, E., Gorelik, T., Kolb, U., et al. (2019). ACS Cent. Sci. 5, 1315−1329.

[2] Brázda, P., Palatinus, L., Babor, M. (2019). Science. 364, 667−669

[3] Spence, J.C.H., Zuo, J.M., O'Keeffe, M., Marthinsen, K., Hoier, R. (1994). Acta. Cryst. A50, 647−650

Support by the Czech Science Foundation (project number 21-05926X), and by Operational Programme Research, Development and Education financed by European Structural and Investment Funds and the Czech Ministry of Education, Youth and Sports (Project No. SOLID21 CZ.02.1.01/0.0/0.0/16_019/0000760) is highly appreciated.

In this talk, I will describe our recent work on the design and preparation of novel supramolecular architectures based on a range of element-based non-covalent interactions such as halogen bonds, chalcogen bonds, and pnictogen bonds. In addition to standard wet chemistry and slow evaporation methods, the utility of mechanochemical and cosublimation techniques will be discussed. Considered together, these methods enable a broad exploration of the polymorphic cocrystalline landscape. For example, the cosublimation approach overcomes an anticooperative halogen-bonding effect to produce fully saturated cocrystals of the tritopic halogen bond donor 1,3,5-trifluoro-2,4,6-triiodobenzene with 1,4-diazabicyclo[2.2.2]octane.¹ I also report on dicyanoselenodiazole and dicyanotelluradiazole derivatives which work as promising supramolecular synthons with the ability to form double chalcogen bonds with a wide range of electron donors including halides and oxygen‐ and nitrogen‐containing heterocycles.² In addition to X-ray diffraction, solid-state multinuclear magnetic resonance (SSNMR) and nuclear quadrupolar resonance (NQR) spectroscopies are employed to characterize all products and to establish spectral signatures for the various classes of bonds. Given the elements involved in these bonds, we report on a wide range of nuclides including e.g., ¹⁷O, ³¹P, ^35/37Cl, ⁷⁷Se, ^79/81Br, ¹²⁵Te, ¹²⁷I, ^121/123Sb, etc. As most of these are quadrupolar nuclides, the utility of specialized NMR techniques and very high applied magnetic fields will be discussed. In favourable cases, in-situ solid-state NMR spectroscopy allows for real-time monitoring of cocrystallization reactions and for the determination of activation energies.³

1. Szell, P. M. J.; Gabriel, S. A.; Caron-Poulin, E.; Jeannin, O.; Fourmigué, M.; Bryce, D. L. Cryst. Growth Des. 2018, 18, 6227. https://doi.org/10.1021/acs.cgd.8b01089

2. Kumar, V.; Xu, Y.; Bryce, D. L. Chem. Eur. J., in press. https://doi.org/10.1002/chem.201904795

3. Xu, Y.; Champion, L.; Gabidullin, B.; Bryce, D. L. Chem. Commun. 2017, 53, 9930.
https://doi.org/10.1039/C7CC05051H

Different crystallization and screening techniques have been developed for the discovery of new multicomponent molecular crystals. Exploring the polymorphic space for a given organic molecule typically includes searches across well-defined conditions, among others solvents, additives, and temperature. In recent years, especially mechanochemistry has been used intensively for the screening for new solid forms and as a promising, alternative method for accessing new polymorphs of active pharmaceutical ingredients (APIs) and API-cocrystals.[1-2] The ever-increasing interest in this method is contrasted by a still limited mechanistic understanding of the mechanochemical reactivity and selectivity. Furthermore, the influence of liquids used during the grinding on the polymorphic outcome is still far from being understood. Time-resolved in situ investigations of milling reactions provide direct insights in the underlying mechanisms.[3-5] We recently introduced different setups enabling in situ investigation of mechanochemical reactions using synchrotron XRD combined with Raman spectroscopy and thermography allowing to detect crystalline, amorphous, eutectic, and liquid intermediates. In this contribution, we will discuss our recent results investigating the formation of (polymorphic) cocrystals and salts, thereby elucidating the influence of solvents and seeds on the polymorph formation.[6-8] Our results indicate that in situ investigation of milling reactions offer a new approach to tune and optimize mechanochemical processes.

A careful investigation of the packing in the nearly 1500 organic, well-refined (R£0.050), P1, Z>1 structures archived in the 2019 version of the Cambridge Structural Database [1] has revealed that the molecules (or ions) in ca. 85% of those structures are related by obvious approximate symmetry that is periodic in at least two dimensions. An example is shown in Fig. 1. The nearly 250 P1, Z=1 structures of molecules that could lie on special positions were also analyzed; ca. 70% were found to have approximate symmetry.

Figure 1. Views of LUSMAN, P1, Z=2 [2]; the second view, of a bilayer, is rotated by 90° around the horizontal from the first. The approximate c211 symmetry of a layer (001) with 0.5 < z < 1.5 (axes [110], [10]; angle 89.9°) is obvious. The angles of those axes with c are 77.8° and 81.8°.

In only 8% of the Z>1 structures does it seem likely that refinement in a higher symmetry space group or smaller unit cell would have been preferable. That percentage is, however, much higher (39%) for P1 crystals of achiral or racemic material, which account for 11% of all Z>1 structures considered. For P1, Z>1 crystals that are enantiomerically pure the frequency of overlooked symmetry is only 2%. For the Z=1 crystals the percentage is 10% overall and 17% for the crystals of achiral or racemic material.

In the abstract of R. E. Marsh’s (1999) paper titled “P1 or P? Or something else?” [3] he wrote
In approximately one-third of the structures in which chiral molecules crystallize in P1 with Z=2, the two molecules are related by
an approximate center of inversion.
The present study found that 32% of the P1, Z=2 structures of enantiomerically pure material are P mimics. Molecular features that promote P mimicry have been identified; they may have implications for the probability of formation of solid solutions.

The approximate symmetry is often subperiodic, as it is in the example shown in Fig. 1. The ratio of structures having 2-D to those having 3-D approximate periodic symmetry is about 2:3 but the ratio is imprecise because of the difficulty of deciding on the dimensionality. In some structures the approximate symmetry is clearly 3-D and in others it is clearly 2-D, but in many others the dimensionality is at the 3-D/2-D borderline. In only 22 structures, however, was the approximate symmetry identified as 1-D. The approximate subperiodic symmetry was described with the labels for layer and rod groups found in Vol. E of International Tables [4].

The surprisingly exact approximate symmetry found in many P1 crystals could result from a distortion during growth or cooling of a more symmetric nucleus, but in more than 3% of the Z>1 structures quite different layers alternate so that the P1 symmetry must have been established at the time of crystal nucleation.

[1] Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016), Acta Cryst. B72, 171-179. [2] Adam, W. & Zhang. A. (2003) Eur. J. Org. Chem. 2003, 587-591. [3] Marsh, R. E. (1999). Acta Cryst. B55, 931-936. [4] Kopský, V. & Litvin, D. B. (2002). Editors. International Tables for Crystallography, Vol. E, Subperiodic groups, Kluwer Academic Publishers, Dordrecht/Boston/London, 2002.

A 47-year-old polymorphic structure (Form δ) of the drug indomethacin (IDM) has been solved by 3D electron diffraction (3D ED). Since its discovery in 1974, the structure of δ-IDM had remained a mystery. By performing a unique crystallisation technique, we successfully cultivated its single crystal. The very thin, ribbon-like crystal was too small (~1 µm in width) to be studied by X-ray diffraction—including even the third generation of synchrotron radiation. With the aid of 3D ED, we finally elucidated the crystal structure of δ-IDM. The structure exhibits a very long b-axis with the slowest growth and shortest crystal dimension occurring along this direction. Consequently, reflections along 0k0 were missing in the 3D ED data and the structure could not be solved by direct methods. Instead, simulated annealing was employed to overcome this problem. This work highlights the powerfulness of 3D ED for structure determination of small crystals, which complements X-ray diffraction.

Non-Photochemical Laser-Induced nucleation (NPLIN) is a promising nucleation technique [1] for which more than eighty papers have been published. In an NPLIN experiment, a supersaturated solution of a molecule is irradiated by a laser (pulsed or continuous, focused or non-focused) that induces the molecule's nucleation. Even though glycine nucleation constitutes almost one-quarter of these research activities reported in the literature, the impact of different experimental conditions on its nucleation is still not fully understood [2]. NPLIN of glycine in water has been demonstrated at different molarities and different energy densities induced using a non-focalized pulsed laser (532 nm) at 290 K. A new index (Ind50), allowing easy comparison with the literature, was used to characterize the impact of molarities and energy densities on the nucleation efficiency. A threshold index (Ind_Thrs(β)) indicating the minimum energy density required to obtain in a given experimental condition one crystal per vials in average has been determined. The impact of the circular or linear polarization of the laser beam on the glycine polymorphism (α- or γ-glycine) has been studied and characterized using a third new index named NPLIN determinant. The experimental interface (glass-solution or air-solution) gives the opposite polymorphism behavior. The relationship between devices, solution, and experimental conditions and observable such as nucleation efficiency, nucleation site, induction time, crystal counting, and polymorphism have been modelized in a mind-map (Figure 1). Within this context, this work is a contribution towards a better understanding of the impact of experimental conditions on NPLIN nucleation that will permit a better design and control of NPLIN experimental setups.

[1] Garetz, B. A.; Aber, J. E.; Goddard, N. L.; Young, R. G.; Myerson, A. S. (1996) Phys. Rev. Lett. 77, 3475−3476.

[2] Clair, B.; Ikni, A.; Li, W.; Scouflaire, P.; Quemener, V.; Spasojević-de Biré, A. (2014) J. Appl. Crystallogr., 47, 1252−1260

Photo-induced electron transfer (PET) reactions are crucial for many biological and chemical reactions that occur in nature. Several studies are performed on many donor-bridge-acceptor (D-B-A) systems to have a better understanding of PET in terms of the rate of transfer and the overall geometry.[1] A mono-substituted pyrene derivative, pyrene-(CH₂)₂-N,N'-dimethylaniline, were designed where dimethylaniline (DMA) (electron donor) is connected to pyrene (electron acceptor) through alkane chain. Two polymorphic crystal forms, A and B, were crystallized in two separate crystallization batches in ethanol/ethyl acetate binary mixture. While, in the crystal structure A, pyrene and dimethylaniline are in axial orientation (P-1) with respect to each other, in B they are equatorial (P2₁/n). Studies on intramolecular PET has revealed the importance of conformational parameters of the molecules such as rotation around bonds that affects the distance and relative orientation of the donor and acceptor.[2] We have performed time-resolved (TR) pump-probe pink Laue X-ray diffraction experiments with the polymorphic crystals in ns time domain. TR pump-probe data was processed by RATIO[3] method by employing LaueUtil software[4]. The photodifference maps obtained from TR pump-probe diffraction measurements with polymorphic crystals, suggest electron transfer from DMA moiety. A thorough crystallographic and spectroscopic investigation with the polymorphic crystals, have allowed us to understand the important aspects of PET in this particular (D-B-A) system.

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

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.

ABO₃ oxides have proven to accommodate a wide variety of chemical compositions, to crystallise with several structures in competition and to develop diverse physical properties. Hence, they are intensively studied in the search for new functional materials. Among them, the use of high-pressure and high-temperature synthesis techniques allows the stabilisation of the small Mn²⁺ cation in the larger A site. Some of the most exciting A-site manganites are spintronic (e.g. perovskite MnVO₃-II) or multiferroic (e.g. LiNbO₃-type MnTiO₃-II) [1,2]. Mixing different cations into the A and/or B sites induces cation order and further magnetic complexity. Recent studies on high pressure Mn₂BB’O₆ compounds have evidenced the accessibility to new structural derivatives, such as the double double perovskite structures (DDPv) or triple perovskites (TPv) with 1:2 order of the B-site cations [3,4]. The possibility to tune both structure and properties as a function of the chemical composition has also been observed, for instance in the Mn_3-xCo_xTeO₆ double perovskite – Ni₃TeO₆-type solid solutions [5].

Here we present a revision on the strongly frustrated magnetic structures of A-site manganites with ordered corundum or perovskite derivative structures (Fig.1). Among the corundum derivatives, magnetic frustration arises as a consequence of the stacking of honeycomb and/or triangular magnetic sublattices. In the case of the perovskite superstructures, it is usually the competition between several magnetic interactions and the combination of dⁿ with d⁰ /d¹⁰ cations what induces large frustration indexes. As a result of such frustration both types of polymorphs develop complex magnetic structures, including incommensurate helices, temperature dependent propagation vectors, elliptical and sinusoidal modulation of the magnetic moments, lock-in spin transitions and split of the main magnetic phase into coexisting ground states.

Figure 1. Representative examples of cation order and magnetic frustration in corundum (a) and perovskite (b) derivatives in high pressure A-site manganites. a) Stacked honeycomb/ triangular sublattices (top left), temperature dependence of the propagation vector in Co₃TeO₆ (right) with split into circular and elliptical helices (bottom left). b) DDPv and 1:2 TPv structures of MnRMnSbO₆ and Mn₃MnNb₂O₉ respectively with several magnetic interactions in competition. Complex thermodiffraction of Mn₃MnNb₂O₉ developing a SDW modulated structure and lock-in transition at low temperatures.

[1] Markkula, M., Arevalo-Lopez, A. M, Kusmartseva, A., Rodgers, J. A. Ritter, C., Wu, H. & Attfield J.P. (2011) Phys. Rev. B. 84, 094450.

[2] Arevalo-Lopez, A. M. & Attfield, J. P. (2013) Phys. Rev. B. 88, 104416.

[3] Solana-Madruga, E., Arévalo-López, A. M., Dos Santos‐García, A. J., Urones‐Garrote, E., Ávila‐Brande, D., Sáez‐Puche, R. & Attfield, J. P. (2016) Angew. Chem. Int. Ed. 55, 9340.

[4] Solana-Madruga, E., Aguilar-Maldonado, C., Ritter, C., Mentré, O., Attfield, J. P. & Arevalo-Lopez, A. M. (2021) Angew. Chem. Int. Ed. Under revision.

[5] Solana-Madruga, E., Aguilar-Maldonado, C., Ritter, C., Huvé, M., Mentré, O., Attfield, J. P. & Arevalo-Lopez, A. M. (2021) Chem. Commun. 57, 2511-2514.

External stimuli such as temperature, electric and magnetic field, light or guest molecules can be used to control the magnetic properties of molecule-based solids. This in turn can lead to interesting magnetic switching behavior.[1, 2] Molecular magnets are also very susceptible to mechanical stress and yet external pressure is rarely used in this field to study magneto-structural correlations. This is most probably caused by a common belief that molecular crystals are mechanically fragile. In fact, they show very good stability under high quasi-hydrostatic conditions even up to 3 GPa, which is sometimes accompanied by astonishing changes/transformations.

Herein a combined structural, magnetic and spectroscopic study of a family of octacyanoniobate(IV)-based molecular magnets {[M^II(pyrazole)₄]₂[Nb^IV(CN)₈]×4H₂O}_n [3] MNb (M = Mn, Fe, Co or Ni) will be presented and discussed. The four compounds are isostructural and exhibit a three-dimensional (3-D) cyanide-bridged framework with a diamond-like topology (Fig. 1). The 3d transition metal ions M define their optical and magnetic properties under ambient pressure: MnNb (yellow) and FeNb (dark violet) are ferrimagnetic with the critical temperatures of 25 and 9 K, while CoNb (dark yellow) and NiNb (greenish) are both ferromagnetic with Curie temperatures of 6 and 13 K, respectively. The MNb family shows also stunning differences in their pressure responses depending on the metal ion M. The MnNb exhibits one of the highest shifts of the magnetic ordering temperature from 24 K to 37 K in response to pressure,[4] FeNb is a pressure-induced spin-crossover photomagnet based on the LIESST effect (LIESST = light induced excited spin state trapping),[4] while the long range magnetic ordering in CoNb switches from ferromagnetic to ferrimagnetic character under pressure. Finally, NiNb shows significant lowering of the Curie temperature under pressure – completely opposite to MnNb.[5] The thorough high pressure magnetic studies of MNb are correlated with the high pressure single-crystal X-ray diffraction structural analysis, enabling a full understanding of the observed pressure-induced changes [4, 5].

Perovskites ABO3 are of great interest due to their large variety of electronic and magnetic properties. Their compositions can be modified to induce different cation orderings giving double perovskites AA’B2O6 or A2BB’O6, and even more complex double double perovskites (AA’BB’O6) [1]. Recently, by using high-pressure and high-temperature (HPHT) techniques, we reported a new type of double double perovskite derivatives (DDPv) where columnar ordering at A-site and rock-salt ordering at B site are combined [2]. These crystallise with space group P42/n and two families have been established; those with R (= rare earth) cations at A sites in RMnMnSbO6 [2]; and those with Ca e.g. CaMnMReO6 (M = Mn, Fe) [3].

We have successfully synthesised a new R-based series of HPHT perovskites, RMnMnTaO6. Large R cations (R = La-Sm) result in a DDPv structure with space group P4₂/n; whereas a disordered A-site DPv structure has been observed for the smaller R =Eu-Y, with space group P2₁/n. By increasing the temperature, a structural transition from DDPv to DPv was observed for the very first time (Fig.1), confirming the structural phase boundary for the RMnMnTaO₆.

Magnetic measurements show a ferrimagnetic ordering for the DDPv and a ferromagnetic ordering for the DPv. Two magnetic transitions with spin reorientation has been found for the DDPv Nd-compound. All information above indicates a very rich structural and magnetic behaviour for the RMnMnTaO₆ family.

[1] King, G., Woodward, P. M. (2010). J. Mater. Chem. 20, 5785.

[2] Solana‐Madruga, E., Arévalo‐López, Á. M., Dos Santos‐García, A. J., Urones‐Garrote, E., Ávila‐Brande, D., Sáez‐Puche, R. & Attfield, J. P. (2016). Angew. Chem. Int. Ed. 55, 9340.

[3] McNally, G. M., Arévalo-López, Á. M., Kearins, P., Orlandi, F., Manuel, P., & Attfield, J. P. (2017). Chem. Mater. 29, 8870.

The compositional flexibility of double perovskites A₂BB’O₆ gives this family of materials a huge range of properties,[1] and interest in accommodating 5d cations such as Os⁶⁺ on a B sites stems from the stronger spin-obit coupling for these heavier cations (compared with 3d transition metal cations). This gives interesting electronic and magnetic properties of these phases and the A₂NiOsO₆ (A = Ca, Sr, Ba) series spans insulating to metallic phases, with ferromagnetic to antiferromagnetic order,[2-4] and with half-metallicity proposed for Sr₂NiOsO₆.[5] These properties are very sensitive to Ni – O – Os bond lengths and angles and therefore to A²⁺ cation size.[2]

The lower symmetry environments favoured by 6s² “inert pair” cations such as Pb²⁺ give structures and properties that can be quite different from those observed for the group 2 A cation analogues.[6, 7] However, high pressure synthetic routes are often required to access these lead analogues.[1]

This presentation describes work on the structural characterisation and properties of Pb₂NiOsO₆ synthesised at high pressure (6 GPa, 1575 K).[8] The rocksalt ordering of NiO₆ and OsO₆ octahedra combined with octahedral tilts gives a crystal structure of P2₁/n symmetry (similar to Ca₂NiOsO₆). Strong coupling between Ni²⁺ and Os⁶⁺ moments gives long-range magnetic order below 58 K, with the collinear magnetic structure described by magnetic propagation vector k = (½ 0 ½) (similar to Pb₂CoOsO₆[6]). This magnetic order, imposed on the (B-site ordered) crystal structure, breaks inversion symmetry.[8]

[1] Vasala, S.; Karppinen, M., (2015), Progress in Solid State Chemistry 43, 1-36.

[2] Morrow, R.; Samanta, K.; Saha Dasgupta, T.; Xiong, J.; Freeland, J. W.; Haskel, D.; Woodward, P. M., (2016), Chemistry of Materials 28, 3666-3675.

[3] Macquart, R.; Kim, S.-J.; Gemmill, W. R.; Stalick, J. K.; Lee, Y.; Vogt, T.; zur Loye, H.-C., (2005), Inorganic Chemistry 44, 9676-9683.

[4] Feng, H. L.; Calder, S.; Ghimire, M. P.; Yuan, Y.-H.; Shirako, Y.; Tsujimoto, Y.; Matsushita, Y.; Hu, Z.; Kuo, C.-Y.; Tjeng, L. H.; Pi, T.-W.; Soo, Y.-L.; He, J.; Tanaka, M.; Katsuya, Y.; Richter, M.; Yamaura, K., (2016), Physical Review B 94, 235158.

[5] Ghimire, M. P.; Hu, X., (2016), Materials Research Express 3, 106107.

[6] Princep, A. J.; Feng, H. L.; Guo, Y. F.; Lang, F.; Weng, H. M.; Manuel, P.; Khalyavin, D.; Senyshyn, A.; Rahn, M. C.; Yuan, Y. H.; Matsushita, Y.; Blundell, S. J.; Yamaura, K.; Boothroyd, A. T., (2020), Physical Review B 102, 104410.

[7] Jacobsen, H.; Feng, H. L.; Princep, A. J.; Rahn, M. C.; Guo, Y.; Chen, J.; Matsushita, Y.; Tsujimoto, Y.; Nagao, M.; Khalyavin, D.; Manuel, P.; Murray, C. A.; Donnerer, C.; Vale, J. G.; Sala, M. M.; Yamaura, K.; Boothroyd, A. T., (2020), Physical Review B 102, 214409.

[8] Feng, H. L.; Kang, C.-J.; Manuel, P.; Orlandi, F.; Su, Y.; Chen, J.; Tsujimoto, Y.; Hadermann, J.; Kotliar, G.; Yamaura, K.; McCabe, E. E.; Greenblatt, M., (2021), Chemistry of Materials 33, 4188-4195.

Due to their specific peculiarities neutrons are a very useful probe for structural studies on various hot topics related to physics, chemistry and mineralogy. The neutron single crystal diffractometer HEiDi at the Heinz Maier-Leibnitz Zentrum (MLZ) offers high flux, high resolution and large q range, low absorption and high sensitivity for light elements. These properties apply in a similar way to its polarized sister diffractometer POLI, which is optimized for detailed studies on magnetic structures.

In 2016 a project was launched in order to allow studies on tiny samples < 1 mm³ and to develop new pressure cells for HEiDi which can be combined with its existing low temperature equipment in order to study structural properties down to temperatures below 10 K, e.g. MnFe₄Si₃ and related magnetocaloric compounds [1]. This work was supported by the Bundesministerium für Bildung und Forschung (BMBF) (grand no. 05K16PA3). As part of this project various neutron-optical components (Cu220-monochromator, solid state collimators, neutron guides) were developed and optimized in order to generate a sufficiently high flux density at the sample location at the wavelength λ = 0.87 Å. Very tiny single crystal samples (down to < 0.1 mm³) were successfully studied using various new diamond anvil cells (DAC) - developed by A. Grzechnik - up to several GPa, either with a panoramic pressure cell in combination with low temperatures [2] or in a transmission pressure cell, which allows simultaneous studies of the same sample using neutron, synchrotron as well as laboratory x-ray sources [3].

Recently, a follow up project has been launched (BMBF No. 05K19PA2) to focus on further improvements of the high pressure capabilities on HEiDi and POLI and the development of optimized pressure cells for further instruments at the MLZ (POLI, DNS and MIRA), namely advanced clamp cells (see corresponding contribution by A. Eich).

[1] A. Grzechnik et al.; Single-Crystal Neutron Diffraction in Diamond Anvil Cells with Hot Neutrons; J. Appl. Cryst. 51, 351-356 (2018).

[2] A. Eich et al.; Magnetocaloric Mn₅Si₃ and MnFe₄Si₃ at variable pressure and temperature; Mater. Res. Express 6, 096118 (2019).

[3] A. Grzechnik et al.; Combined X-ray and neutron single-crystal diffraction in diamond anvil cells; J. Appl. Cryst. 53(1), 1 - 6 (2020).

Frustrated magnets with spiral magnetic phases are currently being intensively studied owing to their ability for inducing ferroelectricity. This could potentially be exploited in spintronics and low power memories devices.[1-2] However, the low magnetic order temperatures (typically < 100 K) in most of frustrated magnets greatly restrict their fields of application. One of the most notable exceptions are Cu/Fe-based layered perovskites, featuring magnetic spiral phases whose ordering temperatures can be continuously tuned far beyond RT. [3-5]. However, the influence of magnetic field on the magnetic structures especially spiral phases, imperative for further cross-control of the magnetic and ferroelectric orders, is barely known.

Here, we report a comprehensive description of the evolution of magnetic order in the layered perovskite YBaCuFeO₅ under the application of magnetic fields up to 9.0 T and at temperatures between 1.5 K and 300 K. Using bulk magnetization measurements and neutron powder diffraction we reveal the existence of a new incommensurate magnetic phase with a weak ferromagnetic component stable at low magnetic fields. Moreover, we observe a field-induced spin reorientation in the collinear phase. The resulting H-T phase diagram of YBaCuFeO₅ will be discussed, with emphasis in the magnetic phases with the largest potential to display strong magnetoelectric effects. [6]

[1] Eerenstein, W., Mathur, N.D. & Scott, J.F. (2006). Nature. 442, 759. [2] Kimura, T., Goto, T., Shintani, H., Ishizaka, K., Arima, T.H. & Tokura, Y. (2003). Nature 426, 55. [3] Morin, M., Scaramucci, A., Bartkowiak, M., Pomjakushina, E., Deng, G., Sheptyakov, D., Keller, L., Rodriguez-Carvajal, J., Spaldin, N.A., Kenzelmann, M., Conder, K. & Medarde, M. (2015). Phys. Rev. B 91, 064408. [4] Morin, M., Canévet, E., Raynaud, A., Bartkowiak, M., Sheptyakov, D., Ban, V., Kenzelmann, M., Pomjakushina, E., Conder, K. & Medarde, M. (2016). Nat. Commun. 7, 1. [5] Shang, T., Canévet, E., Morin, M., Sheptyakov, D., Fernández-Díaz, M. T., Pomjakushina, E. & Medarde, M. (2006). Sci. Adv. 4, eaau6386. [6] Lyu, J. et al. in preparation.

Zeolites represent a unique class of inorganic compounds, which have a simple idealized composition TO₂ and uniform tetrahedral and bridge coordination of the T and O atoms. However, such simplicity gives rise to extremal diversity in the topologies of the zeolite frameworks, which is comparable with the variety of organic compounds: theoretically, the number of the framework topologies is infinite and the databases of hypothetical frameworks generated by computer procedures contain hundreds of thousands of entries. All the more surprising that the number of zeolites existing in nature or obtained in the laboratory is quite modest: currently, in the database produced by the International Zeolite Association there are only 248 topologically distinct zeolite frameworks, which compose less than 0.1% of the known low-energy hypothetical frameworks. Many efforts were undertaken to explain this phenomenon, as well as to predict new zeolite topologies. Paradoxically, most of the proposed explanations of this topological scarcity were based on geometrical or energetic properties of the frameworks, but not on their topological properties. However, low energy of the zeolite framework is not the sufficient proof of its feasibility; no less important are the kinetic factors that drive the framework assembly. While the framework energy is reflected to some extent by the geometrical parameters, which characterize the framework distortion, the assembly of the framework is encoded in its topological parameters. Thus geometry and topology meet to feature the thermodynamics and kinetics of the framework formation.

We explain the feasibility of the zeolite frameworks within the topological model of natural tiling, which represents covering of the crystal space by non-crossing minimal cages (natural tiles) built from the nodes and edges of the framework. We show that the assembling of the framework from natural tiles reflects kinetic factors, which complement the thermodynamic criteria, and explains the inconsistency in the number of hypothetical and realized framework motifs [1]. Moreover, the model of natural tiling enables one to predict more thoroughly new robust zeolite frameworks. We have extended this model and included parts (halves) of tiles into consideration. This extension allowed us to find many hidden relations in the zeolite topological motifs and particularly to interpret and predict the intergrowth phenomena in the zeolite minerals and synthetic phases [2]. Natural tiles can also be considered as building units in modelling crystal growth by Monte Carlo methods [3]. We have implemented the natural tiling model in the ToposPro program package (https://topospro.com) and developed a database of all natural tiles that occur in known zeolite frameworks (TTT collection). This enabled us to explore the natural tilings in hypothetical zeolites and find those of them that could be easily assembled and hence obtained in the experiment. We also apply the tiling model for the purposeful sampling of organic structure directing agents and propose a list of them for a target synthesis of the hypothetical zeolite frameworks.

[1] Kuznetsova, E.D., Blatova, O.A. & Blatov, V.A. (2018). Chem. Mater. 30, 2829.

[2] Golov, A.A., Blatova, O.A. & Blatov, V.A. (2020). J. Phys. Chem. C, 124, 1523.

[3] Anderson, M., Gebbie, J., Hill, A., Farida, N., Attfield, M., Cubillas, P., Blatov, V.A., Proserpio, D.M., Akporiaye, D., Arstad, B., Gale, J. (2017). Nature, 544, 456.

This work was supported by the Russian Science Foundation (Grant No. 16-13-10158).

According to Löwenstein’s rule [1], Al-O-Al bridges are forbidden in the aluminosilicate framework of zeolites. A graph-theoretical interpretation of the rule, based on the concept of independent sets, was proposed by Klee [2] and reviewed by Eon [3]. It was shown that one can apply the vector method to the associated periodic net and define a maximal Al/(Al+Si) ratio for any aluminosilicate framework following the rule; this ratio was called the independence quotient of the net. This presentation deals with practical issues regarding the calculation of the independence quotient of mainly 2-periodic nets and the possible existence of disordered structures with this ratio.

We first show that applying Proposition Calculus to the determination of independent sets in finite graphs leads to introducing a multivariate polynomial, called the independence polynomial. This polynomial can be calculated in an automatic way and provides the list of all maximally independent sets of the graph, hence also the value of its independence quotient. Some properties of this polynomial are discussed; the independence polynomials of some simple graphs, such as short paths or cycles, are determined as examples of calculation techniques.

The determination of the independence quotient of a periodic net requires finding a subgroup of the translation group of the net for which the quotient graph and a fundamental transversal have the same independence quotient. See Fig. 1 for an illustration based on the hbt net, with independence quotient of 4/7; the only maximally independent set in the quotient graph and in the transversal associated to a primitive unit cell is shown in red. In most nets, however, a non-trivial translation subgroup has to be found. We show that this subgroup should be chosen to eliminate every cycle in the quotient graph that is shorter than structural cycles, or rings, of the net. Several examples are then analysed, which show that the choice of the fundamental transversal is critical; no rule, however, can yet be formulated concerning this choice.

The existence of disordered materials with substitution ratio equal to the independence quotient of the respective periodic net is related to the multiplicity of solutions for maximally independent sets of its quotient graph. Some examples are analysed, summarizing different possible situations in 2-periodic nets. The disorder can be complete in two directions or partial and limited to one direction.

[1] Löwenstein, W. (1954). Am. Mineral. 39, 92. [2] Klee, W. E. (1974). Z. Kristallogr. 140, 154. [3] Eon, J.-G. (2016). Struct. Chem. 27, 1613.

[2] Klee, W. E. (1974). Z. Kristallogr. 140, 154. [3] Eon, J.-G. (2016). Struct. Chem. 27, 1613.

[3] Eon, J.-G. (2016). Struct. Chem. 27, 1613.

A 3-fold fabric denoted by , consists of three congruent non-parallel layers of strands in a plane together with a preferential ranking or ordering of the three layers at every point of that does not lie on the boundary of a strand, such that hangs together. The ranking must satisfy the fact that if belongs to a strand of layer and of layer (, ), then if layer is ranked before at , then layer must be ranked before layer at every point of . The fabric hanging together means it is impossible to partition the set of all strands, belonging to all the layers, into two nonempty subsets so that each strand in the first subset passes over (is ranked before, or takes precedence over) every strand in the second subset. The fabric is 3-way, if the strands lie in three different directions in [1].

This paper will discuss symmetry groups of 3-way 3-fold fabrics. The symmetry group of the fabric is a layer group and consists of isometries of the Euclidean space which map each strand of onto a strand of that either preserves the rankings at each point of (preserves the sides of ) or reverses all the rankings (interchange the sides of ). The approach to describe the symmetry group of will be to construct a corresponding design of , which characterizes the fabric in terms of the rankings of the layers.

To represent , we consider on the plane of , sets of equidistant parallel lines to represent the edges (boundaries) of the strands; with lines lying in three different directions. These lines divide into a set of polygonal regions or tiles, each of which is assigned a color indicating the ranking of the layers at every point of the region or tile. The result is a coloring of a tiling which is called the design of , An example of a sketch of a 3-way 3-fold fabric called the mad weave is shown in Figure 1. Its design is shown in Figure 2, given by a 3-coloring of the tiling by triangles. The colors yellow, blue and red represent the rankings (123), (231) and (312) respectively, where the three directions of the strands are represented with vectors at with each other, with labels 1, 2 and 3. is shown in Figure 2. The ranking (123) for example would mean a strand with direction 1 goes over a strand with direction 2, which goes over a strand with direction 3.

The layer group representing the symmetry group of is given by , where each element in will correspond to a symmetry of that either preserves or interchanges the sides of . The elements in that correspond to a symmetry of that preserve the sides of constitute the group , which is of index 1 or 2 in .

For the mad weave we have where , is the counterclockwise rotation centered at the point labeled P, is the horizontal reflection passing through P and are translations with vectors indicated. The group is the color group of and consists of all the elements of the symmetry group of the uncolored triangle tiling that effects a permutation of the colors. On the fabric , there corresponds is a counterclockwise rotation with center at and translations with vectors indicated, that preserve the sides of , and a reflection whose axis is the horizontal line through that reverses its sides.

This paper will discuss all possible layer groups of a 3-way 3-fold isonemal fabric, and give corresponding designs of the fabrics arrived at using color symmetry theory.

Figure 1. The sketch of the mad weave. Figure 2. The design of the mad weave. [1] B. Grünbaum, B., Shephard,G. C. (1998). Isonemal Fabrics. The American Mathematical Monthly 95, pp. 5-30.

Keywords: 3-way 3-fold fabric; layer group; symmetry group; color group; color symmetry

A conventional representation of a periodic crystal by its primitive unit cell and motif is well-known to be ambiguous. Indeed, any crystal can be generated from infinitely many primitive unit cells and motifs containing differently located atoms. Niggli’s reduced cell is unique but discontinuous under perturbations. Continuity of crystal representations is important for filtering out near duplicates in big datasets [1, Fig. 2d] of simulated crystals in Crystal Structure Prediction (CSP). Symmetry groups and many other descriptors discontinuously change under perturbations. So CSP landscapes are plotted only by two coordinates: the structural energy and density.

We describe a new geometric approach to generating a unique code (called a crystal isoset) of any periodic crystal, which continuously changes under perturbations of atoms [2-3]. This isoset is a material genome or a DNA-type code that allows an inverse design of new periodic crystals. Using these complete isosets, one can define numerical invariants via interatomic distances [4] and density functions [5]. For any crystal dataset irrespective of symmetries or chemical compositions, invariant vectors of crystals can be joined in a minimum spanning tree due to continuous distances quantifying crystal similarities. The Python code of distance-based invariants [4] has produced the map of over 12,000 structures from the Cambridge Structural Database overnight on a modest desktop, see Figure 1 in the attached pdf.

[1] Pulido, A., Chen, L., Kaczorowski, T., Holden, D., Little, M.A., Chong, S.Y., Slater, B.J., McMahon, D.P., Bonillo, B., Stackhouse, C.J. and Stephenson, A., 2017. Functional materials discovery using energy–structure–function maps. Nature, 543(7647), pp.657-664.

[2] Anosova, O., Kurlin, V. (2021). An isometry classification of periodic point sets. Peer-reviewed proceedings of Discrete Geometry and Mathematical Morphology, available at http://kurlin.org/research-papers.php#DGMM2021.

[3] Anosova, O., Kurlin, V. (2021). Introduction to Periodic Geometry and Topology. Available at https://arxiv.org/abs/2103.02749.

[4] Widdowson, D., Mosca, M., Pulido, A., Kurlin, V., Cooper, A.I. (2021). Average Minimum Distances of a periodic point set. Available at https://arxiv.org/abs/2009.02488.

[5] Edelsbrunner, H., Heiss, T., Kurlin, V., Smith, P, Wintraecken, M. (2021). The density fingerprint of a periodic point set. Peer-reviewed proceedings of Symposium on Computational Geometry. Available at http://kurlin.org/research-papers.php#SoCG2021.

Keywords: crystal similarities; maps of crystal datasets; crystal structure prediction; continuous classification of crystals

We thank all our co-authors of the joint papers above and all reviewers in advance for their valuable time and helpful suggestions.

Intriguing magnetic behaviour has been studied in perovskite structure type materials with the generic formula ABO₃ for decades. Here, A is usually an alkaline earth metal, or a rare earth element, while B is typically a transition metal. In the related double perovskite structure, two different B cations alternate in a rock salt ordering pattern, leading to the general formula A₂BB´O₆ [1]. One of the common features in perovskites is the tilting of the octahedra. As an effect, it tunes the band width of multiple orbitals and the strength and sign of the more typical exchange interactions.

The B-site ordered double-perovskite oxides, where A is Sr or Ba, B is Cu and B‘ is a diamagnetic hexavalent ion, crystallize in a tetragonal structure with short Cu-O bonds in the ab plane and long Cu-O bonds along the c axis, due to the cooperative Jahn-Teller effect of the octahedrally coordinated d⁹ Cu²⁺ ion. While structurally three dimensional, many of these compounds show low-dimensional magnetic properties [2].

The purpose of our study is to find and investigate high degeneracy frustrated magnetically correlated materials. Sr₂CuTe_0.5W_0.5O₆ has recently been reported as a spin-liquid, where the random distribution of Te occupying d-shell on the W (empty d-shell) position blocks a key superexchange path [3]. So, the main goal of this work was to investigate the nearby phase diagrams with the aim of searching new materials with interesting properties and promising characteristics.

Systematically spaced compositions were attempted in polycrystalline solid state reactions for Ba_xSr_2-xCuTe_0.5W_0.5O₆ and Sr₂Cu(Te_xMo_1-x)O₆ systems at atmospheric pressure. These efforts were characterized by X-ray diffraction and SQUID magnetometry where successful, and these results as well as future plans will be presented.
[1] Vasala S., Karppinen M. (2015). Prog. Solid State Chem. 43, pp. 1-36.
[2] Todate Y., Higemoto W., Nishiyama K., Hirota K. (2007). J. Phys. and Chem. of Solids, 68, 11, pp. 2107-2110.
[3] Mustonen O., Vasala S., Sadrollahi E., Schmidt K. P., Baines C., Walker H. C., Terasaki I., Litterst F. J., Baggio-Saitovitch E. & Karppinen M. (2018). Nat. Commun. 9, 1085, pp. 1-8.

When designing food products, it is important to understand and predict structure-function-property relationships within food constituents. This includes knowledge of not only the structure of native materials but also their structural changes across a wide range of length scales brought about by food processing. The inherent complexity of food systems therefore calls for an arsenal of techniques and instrumentation that can access a broad range of dimensions.

The Australian Nuclear Science and Technology Organisation (ANSTO) commenced the ‘Food Materials Science Programme’ to explore opportunities for the utilisation of the nuclear based methods, including small and ultra-small angle neutron scattering ((U)SANS), in a quest to extend the understanding of complex food systems. This presentation will highlight the role of (U)SANS in the context of broader materials characterisation methods, using several examples^1-8.

[1] Elliot Paul Gilbert, Current Opinion in Colloid & Interface Science 42 (2019) 55.

[2] Amparo Lopez-Rubio, Elliot Paul Gilbert, Trends in Food Science and Technology 20 (2009) 576.

[3] James Doutch, Mark Bason, Ferdi Franceshcini, Kevin James, Douglas Clowes, Elliot P. Gilbert, Carbohydrate Polymers 88 (2012) 1061.

[4] Constantinos V. Nikiforidis, Elliot Paul Gilbert, Elke Scholten, RSC Advances, 5 (2015) 47466.

[5] Zhi Yang, Xu Xu, Ravnit Singh, Liliana de Campo, Elliot P. Gilbert, Zhonghua Wu, Yacine Hemar, Carbohydrate Polymers, 212 (2019) 40-50

[6] Yaiza Benavent-Gil, Cristina M. Rosell and Elliot P. Gilbert, Food Hydrocolloids 112 (2021) 106316.

[7] Steven Cornet, Liliana de Campo, Marta Martinez-Sanz, Elke Scholten and Elliot Paul Gilbert, in manuscript

[8] https://www.ansto.gov.au/research/programs/other/food-science

Majority of recent small-angle X-ray scattering (SAXS) studies have been performed mainly in the large-facility, such as SPring-8 (JAPAN), APS (USA), and other synchrotron radiation facilities. Since high intensity of those source makes possible to realize time resolve measurements in a few seconds in non-distractive mode, "operand" measurements become popular and important to understand formation of nanostructures in many materials. In contrast, laboratory SAXS systems are usually regarded as the tool for static measurements. However, recent progress in source, optics (confocal mirror, low scattering slit) and detector makes us possible to measure nanostructure in a few minutes. Those systems can also be optimized for high energy source such as Mo solid or In-rich liquid metal targets. Combining these features, reaction continuing for a few days can be monitored non-destructively, which we call "slow operand" measurements. Two examples will give in this talk; First one is about low temperature aging (room temp., 65ºC, 120ºC) of Al-Zn-Mg-Cu alloys for 2 days. Second example is shape change of colloidal calcium phosphate (CCP) in real cheese for more than 5 days. In the former case, we have measured 1 mm thick aluminum sheet directly from solid solution treatment (SST) without any sample thinig using labo-SAXS with Mo source. We have also measured the sample with rolling following SST. Since all has been done in same room, the uncovered time before starting measurements are less than 5 minutes. Advantage in the second example is the physical distance between source and cheese factory. Since fresh curd (before salting) and cheese has been carried from real cheese factory in Rakuno Gakuen Univ. to labo. SAXS in Hokkaido Univ. with in 1 hour. Samples (curd or cheese) with 1.8 mm thick put into the glass cell and sealed. Shape of nanostructure of cheese corresponding to CCP changes from about sphere of 2.4 nm in diameter to disc like shape with 14 nm in diameter as shown in Fig.1.

Though there are many studies using SAXS [1, 2] including operand measurements in both case, such long time-span measurements have not been reported as far as we know. Nevertheless, there are several processes which are industrially important and occur slowly around room temperature. For those target, the slow operand technique with labo-SAXS must be very useful and important in addition to regular operand technique with large facilities.

Figure 1. Time evolution of SAXS profiles of curd and cheese from 1 hour to 5 days after production . [1] ex. Deschamps, A., De Geuser, F., Horita, Z., Lee, S. & Renou, G., (2014). Acta. Mater. 66, 105[2] ex. Ingham, B., Smialowska, A., Kirby, N. M., Wang, C. & Carr, A. J. (2018). Soft Matter. 14, 3336.

Additive manufacturing (AM) of metals provides great flexibility in manufacturing parts with complex geometrical shapes and is fast becoming an attractive option for the fabrication of high-valued metal components in aerospace, oil & gas, and biomedical industries. The rapid heating and cooling during AM fabrication, which by nature is a highly nonequilibrium process, often leads to significant microstructural heterogeneity uncommon to wrought and cast alloys. Such heterogeneity creates tremendous challenge in the qualification and eventual certification of AM metal parts for many applications.

Using a combination of in situ synchrotron-based X-ray scattering and diffraction methods, ex situ electron microscopy, atom-probe tomography, and thermokinetic and thermodynamic modelling, we have focused on the development of post-build heat treatment protocols for AM alloys. Our established protocols recover the designed phase composition of two types of widely used commercial AM alloys, a major step towards their part certification. Specifically, our work on AM nickel-based superalloy Inconel 625 demonstrates the importance of understanding the effect of elemental microsegregation, a ubiquitous phenomenon in AM alloys resulting from rapid solidification, on the structure and microstructure evolution during post-build heat treatments [1]. Our simulation-constructed and experiment-validated time-temperature-transformation diagram clearly demonstrates the acceleration (by a factor of 100 – 1000) of formation kinetics of a phase deleterious to the fatigue performance of this alloy [2, 3]. Our work on nitrogen-atomized 17-4 stainless steel shows that the starting powder chemistry and compositional partition during solidification results in the as-fabricated 17-4 being fully austenitic, as opposed to being fully martensitic as designed. Our three-step heat treatment protocol successfully recovers the martensitic structure of parts fabricated using nitrogen-atomized 17-4 powders [4]. We also determined the optimal ageing heat treatment to yield optimal strength of this precipitation-hardening alloy.

Our work points to a common and important theme that post-build heat treatment is critical for producing AM alloys with predictable and reproducible microstructures and hence materials properties. The emphasis of proper post-build heat treatment cannot be overstated for the certification of many AM alloys. We also emphasize that rigorous and in situ bulk structure and microstructure measurements only available at synchrotrons are essential for modelers to validate AM simulations for the advancement of AM technologies [5].

References:

[1] Zhang, F., Levine, L. E., Allen, A. J., Stoudt, M. R., Lindwall, G., Lass, E. A., Williams, M. E., Idell, Y. & Campbell, C. E. (2018). Acta Materialia 152, 200-214.

[2] Stoudt, M. R., Lass, E., Ng, D. S., Williams, M. E., Zhang, F., Campbell, C. E., Lindwall, G. & Levine, L. E. (2018). Metallurgical and Materials Transactions A 49, 3028-3037.

[3] Lindwall, G., Campbell, C., Lass, E., Zhang, F., Stoudt, M. R., Allen, A. J. & Levine, L. E. (2019). Metallurgical and Materials Transactions A 50, 457-467.

[4] Lass, E. A., Zhang, F. & Campbell, C. E. (2020). Metallurgical and Materials Transactions A, 1-15.

[5] Zhang, F., Levine, L. E., Allen, A. J., Young, S. W., Williams, M. E., Stoudt, M. R., Moon, K.-W., Heigel, J. C. & Ilavsky, J. (2019). Integrating Materials and Manufacturing Innovation 8, 362-377

Acknowledgement:

Portions of this research were performed on beamline 9-ID-C, 11-ID-B, and 11-BM at the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Nanofluids, i. e. liquids containing dispersed nanoparticles, are gaining increasing interest since the first use of this designation by Choi in 1995 [1]. The primary application for heat transfer as a thermally conductive fluid for cooling is nowadays expanding to sensors, lubricants, magnetic sealing or solar energy collectors. The unique properties of nanofluids arise from the synergy between nanoparticles and the surrounding medium. Our study concerns Ag and Au nanoparticles which belong to plasmonic nanoparticles with the localized particles plasmon resonance (LPPR) in the region of visible light which makes them and their colloidal suspensions attractive for optical applications.

There are numerous preparation methods of nanofluids, among them the very straightforward and solvent-free is magnetron sputtering of metals on the surface of vacuum-compatible liquids (oils, ionic liquids, and polymers). In this method nanoparticles are formed at the vacuum-liquid interface [2]. In our work, the nanoparticle synthesis takes place in the gas phase prior to their landing onto the liquid. Silver and gold nanoparticles were prepared using a magnetron-based gas aggregation cluster source and subsequently deposited into liquid polyethylene glycol (PEG).

The main aim of our study is to determine the stability of Ag and Au nanoparticle dispersions in PEG and to understand the post-deposition processes inside the nanofluids comprising nanoparticles prepared by aggregation from the gas phase. Solutions with different mass concentration of nanoparticles were prepared by controlling the deposition time reaching tens of mg/ml, a value typical for commercially-available Ag colloidal solutions. To investigate the size distributions and interactions between nanoparticles inside the colloidal suspensions the small angle x-ray scattering (SAXS) was used. We performed SAXS measurements repeatedly during six months to determine the suspension stability. The x-ray diffraction proved the crystalline nature of nanoparticles and also the changes in the amount of material dispersed in the suspension. The optical properties of individual suspensions were analyzed by UV-Vis spectroscopy. TEM and SEM measurements of nanoparticles separated from the suspensions were performed to validate the results obtained by the scattering methods.

Prepared Au nanoparticles have bimodal size distribution with mean sizes 13 nm and 40 nm and the corresponding absorption peak associated to the LPPR is observed around 550 nm in the UV-Vis spectrum. In the case of Ag nanoparticles dispersion, UV-Vis spectroscopy shows the maximum corresponding to the LPPR of individual separated nanoparticles around 410 nm and another maximum at larger wavelengths corresponding to nanoparticles aggregates for freshly prepared samples. This observation was further confirmed by SAXS, the mean size of single nanoparticles is around 10 nm and the nanoparticles interact through the hard-sphere interaction. The hard-sphere volume fraction however decreases in time and after two months is not detectable anymore. The resultant suspension exhibited characteristic plasmonic colour in the yellow/orange range and is expected to be stable over extended periods due to constrained mobility of PEG’s macromolecular chains.

[1] Choi, S. U. S., & Eastman, J. A. (1995). American Society of Mechanical Engineers, 231 (March), 99–105.

[2] Wender, H., Gonçalves, R. V., Feil, A. F., Migowski, P., Poletto, F. S., Pohlmann, A. R., Dupont, J., & Teixeira, S. R. (2011). Journal of Physical Chemistry C, 115(33), 16362–16367.

This study was financed by the Grant Agency of Charles University (grant 1546119), by the Czech Science Foundation (grant GACR 21-12828S) and by ERDF in the frame of the project NanoCent - Nanomaterials Centre for Advanced Applications (Project No. CZ.02.1.01/0.0/0.0/15_003/0000485).

The Pb(Zn1/3Nb2/3)O3-4.5PbTiO3 (PZN-4.5PT) single crystals showed very large ferroelectric and piezoelectric properties compared to traditional ferroelectric ceramics (BaTiO3 and PZT) used presently as active material in medical imaging, detection and sonars. However, despite these excellent properties, the greatest difficulty to use PZN-4.5PT single crystals on electronic devices is to achieve them in thin layers form because of their incongruent melting property. To overcome this difficulty, we deposit them as thin layers by dispersing their nanoparticles in a gel containing a matrix that can maintain at least their bulk properties. After this size reduction at nanoscale and the annealing process following the deposition, changes and structural transformations would occur. We fabricate with success thin films by dispersing these nanoparticles in a gel. The materials show some agglomeration at the surface of the silicon substrate films (from SEM images) and non-identified hexagonal microcrystals, which could be at the origin of their excellent properties.

In this paper we use the combined USAXS/SAXS/WAXS instrument at 9ID beamline at APS-ANL for in situ characterization of undoped and 1% Mn doped PZN-4.5PT inorganic perovskite nanoparticles thin films deposited on nanostructured silicon to understand the phases transitions and determine the observed hexagonal microcrystals structure. It revealed a hexagonal structure of the nanoparticles thin films, which could be explained by the new phase that can be assigned to the Pb3(PO4)2 based component. The peak at 31° indicates the presence of the rhombohedral phase perovskites assigned to the nanoparticles. XRD spectra, Raman and EDX mapping are compared to the USAXS, SAXS and WAXS results. WAXS characterization permitted to identify three phase transitions during thermal annealing confirming dielectric permittivity temperature phases transitions.

Complex liquid mixtures are the foundation of industrial products from personal care products to biotherapeutics to specialty chemicals. While small- and wide-angle reciprocal space methods (SANS, SAXS, WAXS) are workhorse techniques for characterizing model formulations, the large number of components (10-100) in many real products often prevents rational mapping between component fractions, structure, and product stability. To enable rational design of these materials, we must leverage theory, simulation, multimodal characterization and machine learning (ML) tools to greatly reduce the expense of exploring the stability boundaries of a particular, desirable phase. Applying ML tools to scattering experiments requires a platform capable of autonomously synthesizing and characterizing samples with varying composition and chemistry. While there are numerous examples of robots which perform specific user facility operations, these systems tend to be bespoke and non-adaptable to new tasks. We have developed a highly adaptable platform that can be programmed to autonomously prepare and characterize liquid-formulations using neutron and X-ray scattering in addition to offline techniques such as optical imaging, UV/vis/NIR, viscometry, etc. Here we will highlight the design of the platform and our latest results in autonomous stability mapping of model formulations from personal care, biopharmaceutical, and alternative energy partner companies.

Spin chain oxides containing cobalt and manganese whose structure is closely related to the 2H hexagonal perovskite [1-5] offer a very attractive field for the investigation of magnetic and multiferroic properties. The structure of the prototypic one-dimensional manganate and cobaltate Sr₄Mn₂CoO₉ consists of chains of face-sharing MnO₆ octahedra and trigonal CoO₆ prisms. According to the very important study performed by Perez-Mato et al [2], these spin chain oxides can be described as a composite 2H hexagonal perovskite family A_1+x(Mn_1-Co_x)O₃. Recently the possibility of extra oxygen incorporation during synthesis has been evidenced leading to a large family aperiodic chain structures [6] expressed by the simple formal formula Sr_1+x(Mn_1-xCo_x)O_3+δ; it induces a decrease of the proportion of the number of trigonal prismatic sites (N_P) with respect to the octahedral sites (N_O) within the chains as δ increases and concomitantly the formation of cobalt vacancies on the trigonal prismatic sites. Therefore the structural formula of these oxides must be expressed as Sr_1+y[(Mn_1-xCo_x)_1-z◊_z]O₃.]

The air-synthesized oxide x=3/8-Sr_1+x(Mn_1-xCo_x)O_3+δ is of great interest, since by decreasing the oxygen over stoichiometry to δ=0, one should obtain the oxide “Sr₁₁Mn₅Co₃O₂₄”(x=y, z=0) expected to be built up of trimeric and dimeric polyhedral units according to the sequence [Sr₄Mn₂CoO₉]₂.[Sr₃CoMnO₆]. Such an oxide containing exclusively strontium was never synthesized in air due to the partial oxidation of Co²⁺ into Co³⁺, imposing δ>0. We then have investigated the substitution of calcium for strontium in the pure Sr-phase x=3/8 (δ_~0.09). The objective was to design composite structures built up of trimeric and dimeric units by decreasing δ down to zero through Ca for Sr substitution in order to finally obtain the stoichiometric oxide A₁₁Mn₅Co₃O₂₄ (A=Sr,Ca). We report herein on a series of A_11/8(Mn_5/8Co_3/8)O_3+δ oxides with composite structures, commensurate or incommensurate, built up of trimeric M₃O₉ and dimeric M₂O₆ units (M= Mn, Co, o) with cationic vacancies on the trigonal prismatic sites. We also show the possibility to synthesize the quasi commensurate stoichiometric composite Sr_4.2Ca_6.8[Mn₂CoO₉]₂.[MnCoO₆] (δ=0.002).

[1] J. Darriet, M.A. Subramanian, J. Mater. Chem. 5 (1995) 543-552.

[2] J.M. Perez-Mato, M. Zakhour-Nakhl, F. Weill, J. Darriet, J. Mater. Chem. 9 (1999) 2795-2807.

[3] K. Boulahya, M. Parras, J.M. Gonzalez-Calbet, J. Solid State Chem. 145 (1999) 116-127.

[4] K.E. Stitzer, J. Darriet, H.-C. zur Loye, Curr. Opin. Solid State Mater. Sci. 5 (2001) 535-544.

[5] H.-C. zur Loye, Q. Zhao, D.E. Bugaris, W.M. Chance, Cryst. Eng. Commun. 14 (2012) 23-39.

[6] Caignaert V, Perez O, Boullay P, Seikh MM, Sakly N, Hardy V, Raveau B, J. of Mater Chem. C 8 (2020) 14559-14569

Diffraction enhancement of symmetry (DES) is a phenomenon by which the space-group symmetry suggested by the diffraction pattern of a crystal is higher than the space-group symmetry of the structure that has produced it [1-5]. The most well-known example is that of Friedel’s law, which is however realized only when resonant scattering is not taken into account. In modular structures, DES does occur also when considering resonant scattering. We address this phenomenon in monoarchetypal modular structures [6]. The condition for DES to occur is that both the module and the vector set (set of all interatomic vectors) [7] are invariant under an isometry that is not a symmetry operation for the structure. Only τ-isometries [8], i.e. isometries that do not reverse the polarity of the stacking vectors, can lead to DES once resonant scattering is taken into account. The example of SiC polytypes, where the phenomenon has been confirmed experimentally, is studied in detail. The SiC layer has symmetry p6mm (diperiodic group); the stacking of SiC layer leads to many polytypes, rapidly increasing in number with the number of layers defining the period along to stacking direction. These polytypes can occur in four types of space group: F-43m, R3m P6₃mc and P31m. If the vector set exhibits hexagonal symmetry, than the space group of the polytype can be either of type P6₃mc or of type P31m. In both cases, the diffraction pattern shows hexagonal symmetry although in the latter case the structural symmetry is only trigonal: DES is thus observed. The number of polytypes showing DES increases rapidly with the number of layers, but the fraction of these polytypes with respect to the total number of polytypes decreases. These conclusions apply as well to all modular structures built by layers of the same symmetry, like ZnS.

[1] Iwasaki, H. (1972). On the Diffraction Enhancement of Symmetry. Acta Cryst. A28, 253-260.

[2] Perez-Mato, J. M. and Iglesias, J.E. (1974). Acta Cryst. A33, 466-474.

[3] Sadanaga, R. and Ohsumi, K. (1975). Proc. Japan Acad. 51, 179-183.

[4] Sadanaga, R. and Ohsumi, K. (1979). Acta Cryst. A35, 115-122.

[5] Iglesias, J. E. (1979). Z. Kristallogr. 150, 279-285.

[6] Ferraris, G.. Makovicky E. and Merlino, S. (2008). Crystallography of Modular Materials. Oxford: Oxford University Press, 384 pp..

[7] Buerger, M. J. (1950). Acta Cryst. 3, 87-97.

[8] Dornberger-Schiff, K. and Grell-Niemann H. (1961). Acta Cryst. 14, 167-177.

Polytypism in cronstedtite; how various stacking sequences of layers affect diffraction pattern Jiří Hybler¹,

¹Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, CZ-18224 Prague 8, Czech Republic

hybler@fzu.cz

The 1:1 layered silicate cronstedtite (Fe²⁺_3-x Fe³⁺_x)(Si_2-xFe³⁺_x)O₅(OH)₄, of the serpentine-kaoline group forms relative large amount of polytypes. They are subdivided into four OD subfamilies, or Bailey’s groups A, B, C, D according to different stacking rules of identical (structure building) 1:1 layers (equivalents of OD packets) with trigonal protocell a=5.5, c=7.1 Å. Distributions of so called subfamily reflections along the reciprocal lattice rows [2l]* / [11l]* / [2l]* in (l_hex)* / (hhl_hex)* / (2hl_hex)* planes of diffraction pattern is used for subfamily determination. Similarly, distributions of characteristic reflections along [10l]* / [01l]* / [1l]* rows in (h0l_hex)* / (0kl_hex)* / (hl_hex) planes allow determination of particular polytypes. For this purpose, graphical identification diagrams simulating distribution of reflections along named rows are used [1]. Owing modern diffractometers with area detectors and appropriate software, and/or Electron Diffraction Tomography (later EDT) technique, precession-like images of Reciprocal Space (later RS) sections corresponding to above listed planes can be easily and quickly obtained.

Lot of specimens of cronstedtite from various terrestrial localities and synthetic run products were studied by the author [1-5]. RS sections were recorded, and selected ones are presented in the lecture in order to demonstrate the variability of diffraction pattern.

In the subfamily A, the stacking rule comprises ±a_i/3 shifts of consecutive layers. The most common is the 3T, relatively rare are 1M and 2M₁ polytypes. They usually occur in 3T+1M, 3T+2M₁, 1M+2M₁ mixed crystals. Monoclinic polytypes might be affected by twinning by reticular merohedry with 120º rotation as twinning operation. Six-layer 6T₂ and three-layer triclinic 3A polytypes are rare. Another possible twinning by 60º rotation changes obverse setting of the subset of subfamily reflections into the reverse one [1, 4].

In the subfamily D, the stacking rule is characterized by alternating 180º rotations of consecutive layers, combined by ±b/3 (of the orthohexagonal cell) or zero shifts. The most common polytypes are 2H₁ and 2H₂, occurring either isolated or in mixed crystals. Rarely, several six-layer polytypes were found. They usually occur in mixed crystals containing more polytypes, up to six! Diffraction patterns of such crystals are, of course, confusing. Fortunately, in many cases polytypes were isolated simply by cleaving crystals into smaller fragments, later studied separately. Hall et all. [6] derived 24 possible sequences of six-layer polytypes of subfamily D serpentines, valid also for cronstedtite. Their diffraction patterns were modelled, and compared with real RS sections. This simulation revealed, that five pairs of sequences (No. 4+6, 7+18, 8+10, 9+13, 11+12) provided identical diffraction patterns. Polytypes really found correspond to following sequences: 1 (Hall’s 6T₁), 5 (proposed 6T₃), 8+10 (6T₅), 11+12 (6T₄), 24 (6T₆) (trigonal polytypes), 22 (6R₁), 23 (6R₂), (rhombohedral polytypes). The hexagonal polytype 6H₂ corresponding to the sequence 14 was also found. However, the identical diffraction pattern can be produced by the obverse-reverse twin of the rhombohedral polytype 6R₂ (sequence 23).

Mixed crystals of polytypes belonging to different subfamilies were rarely found. 1M+1T mixed crystal of subfamilies A and C, respectively, was identified by EDT in the synthetic material [1]. The C subfamily is characterized by mere ±b/3 or zero shifts, without any rotation. The mixed crystals of A+D subfamilies were found in some terrestrial samples. Sometimes, the A and D parts of such crystals were separated by cleaving into smaller fragments.

Many RS sections showed diffuse streaking of characteristic reflections along c* due to partial stacking disorder. In extreme cases, reciprocal lattice rows are completely replaced by diffuse streaks.

The total number of ascertained polytypes of cronstedtite, recognized in RS sections, is 15 (+ one questionable).

[1] Hybler, J., Klementová, M., Jarošová, M., Pignatelli, I., Mosser-Ruck, R., & Ďurovič, S. (2018). Clays and Clay Minerals 66, 379–402.

[2] Hybler, J., Sejkora, J., & Venclík, V. (2016). European Journal of Mineralogy, 28, 765–775.

[3] Pignatelli, I., Mugnaioli, E., Hybler, J., Mosser-Ruck, R., Cathelineau, M., & Michau, N. (2013). Clays and Clay Minerals 61, 277–289.

[4] Hybler, J., Števko, M., & Sejkora, J. (2017). European Journal of Mineralogy, 29, 91–99.

[5] Hybler, J., Dolníček, Z., Sejkora, J., & Števko, M., (2020). Clays and Clay Minerals 68, 632-645.

[6] Hall, S. H., Guggenheim, S., Moore, P., & Bailey, S. W. (1976). Canadian Mineralogist 14, 314-321.

Keywords: cronstedtite; polytypism; layer stacking; X-ray diffraction; electron diffraction tomography

Even after decades of solid-state research, there are intriguing binary systems lacking investigation, even exclusively with main group elements. For instance, there are significantly fewer investigations on beryllium compounds than on any other class of light-element materials, even though beryllium-containing phases feature interesting properties for basic and applied research.[1] Owing to its toxicity, efforts to understand the chemistry of Be are rather rare. However, the limited knowledge present promises a rich and unusual structural chemistry. The few results concerning Be compounds with group 15 elements include the disordered diamond-like structure of BeP₂.[2] Yet, the true building blocks, i.e. the arrangement of polyphosphide anions, remained elusive with respect to the description of the average structure. Preliminary work on BeAs₂ and BeSb₂ indicates related structures for both compounds;[3] however, this information is only based on qualitative evaluation of powder X-ray diffraction data. Precise structural data require very accurate diffraction data due to the large difference in scattering factors. Despite the simple stoichiometry, a complete structural analysis proved difficult as the crystals obtained are by far too small for data collection using laboratory diffractometers. We now employed a combined approach using microfocused synchrotron radiation, electron diffraction and HRTEM.

Synchrotron data of a microcrystal of BeSb₂ reveal a coloring variant of the cubic diamond structure (Fig. 1). The corresponding tetragonal superstructure contains twisted chains of Sb atoms interconnected by Be atoms with all atoms showing a distorted tetrahedral coordination. The conformation of the polyanion corresponds to the Ge substructure in Li_~3AgGe₂.[4] This indicates chemical bonding according to a Zintl phase with a “sulfur-like” Sb^- polyanion (comparable to Ge^2-). Yet, BeSb₂ can also be viewed as a Grimm-Sommerfeld semiconductor with an average valence electron concentration of 4. Compared to Be₁₃Sb, which features Be₁₂ icosahedrons in analogy to the NaZn₁₃ type, the bonding situation changes from quasi-molecular entities to typical semiconductors upon varying the relative Be content. Hypothetical intermediate structures may exhibit rather unusual chemical bonding.

For BeP₂ and BeAs₂, our investigations have confirmed the disordered diamond-like / sphalerite-like structures according to the average structures in literature, which can be refined in space group I4₁/amd.[2,3] Diffraction patterns (both with X-rays and electrons, Fig. 2) exhibit pronounced diffuse streaks that indicate stacking disorder. Synchrotron data were collected from microcrystallites on TEM grids that were pre-characterized by electron microscopy. Both the evaluation of synchrotron diffraction data and HRTEM imaging reveal the nature of the disorder and the local structure of the polyanions. Stacking probabilities were derived by simulation diffraction patterns. The degree of ordering varies: diffuse streaks can be almost uniform but, especially in the case of BeAs₂, they may also approach a superstructure.

[1] M. R. Buchner, R. Pöttgen, H. Schmidbaur (2020). Z. Naturforsch. 75b, 403.

[2] P. L’Haridon, J. David, J. Lang, E. Parthé (1976). J. Solid State Chem. 19, 287.

[3] R. Gerardin, J. Aubry (1976). J. Solid State Chem. 17, 239.

[4] A. Henze, V. Hlukhyy, T. F. Fässler (2015). Inorg. Chem. 54, 1152.

Discrete polyoxometalates: from geochemistry via crystal engineering to functional materials

U. Kortz

Jacobs University, Department of Life Sciences and Chemistry, Campus Ring 1, 28759 Bremen, Germany u.kortz@jacobs-university.de

Polyoxometalates (POMs) are a class of discrete, anionic metal-oxides with an enormous structural diversity and a multitude of interesting properties leading to potential applications in different areas including catalysis, nanotechnology and medicine [1]. Noble metal-containing POMs are in particular attractive for homogeneous and heterogeneous catalytic applications. However, the number of well characterized noble-metal POMs is rather small [2]. POMs based exclusively on Pd²⁺ addenda (polyoxopalladates, POPs) were discovered in 2008 [3]. The area of POP chemistry has developed rapidly ever since, due to the fundamentally novel structural and compositional features of POPs, resulting in unprecedented electronic, spectroscopic, magnetic, and catalytic properties [4]. In terms of POP structural types, the symmetrical 12-palladate nanocube {MPd₁₂L₈} and the 15-palladate nanostar {MPd₁₅L₁₀} are the most abundant. Especially for the {MPd₁₂L₈} nanocube, many derivatives with various central guests including d and f block metal ions and various capping groups are known [4]. We demonstrated the use of {MPd₁₂L₈} as discrete molecular precursors for the formation of supported palladium metal nanoparticles as hydrogenation catalysts, and we discovered an important dependence of the catalytic properties on the type of internal metal guest and external capping group [5]. We also managed to construct 3D coordination networks using externally functionalized POPs, resulting in metal-organic framework (MOF)-type assemblies (POP-MOFs) with interesting sorption and catalytic (C-C coupling) properties [6].

[1] Pope, M. T. (1983). Heteropoly and isopoly oxometalates. Springer Verlag.

[2] Izarova, N. V.; Pope, M. T.; Kortz, U. (2012). Angew. Chem. Int. Ed. 51, 9492.

[3] Chubarova, E. V.; Dickman, M. H.; Keita, B.; Nadjo, L.; Mifsud, M.; Arends, I. W. C. E.; Kortz, U. (2008). Angew. Chem. Int. Ed. 47, 9542.

[4] Yang, P.; Kortz, U. (2018). Acc. Chem. Res. 51, 1599.

[5] Ayass, W. W.; Miñambres, J. F.; Yang, P.; Ma, T.; Lin, Z.; Meyer, R.; Jaensch, H.; Bons, A.-J.; Kortz, U. (2019). Inorg. Chem. 58, 5576.

[6] Bhattacharya, S.; Ayass, W. W.; Taffa, D. H.; Schneemann, A.; Semrau, A. L.; Wannapaiboon, S.; Altmann, P. J.; Pöthig, A.; Nisar, T.; Balster, T.; Burtch, N. C.; Wagner, V.; Fischer, R. A.; Wark, M.; Kortz, U. (2019). J. Am. Chem. Soc. 141, 3385.

Titan, the largest moon of Saturn, has been revealed by the Cassini-Huygens mission to be a fascinating and quite Earth-like world. Among the parallels to Earth, which includes the lakes, seas, fluvial and pluvial features on its surface, is an inventory of organic minerals [1]. However, where on Earth these organic minerals are only found in niche environments, on Titan they are likely to be the dominant surface-shaping materials. Titan’s organic minerals are formed primarily from photochemistry induced by UV radiation and charged particles from Saturn’s magnetosphere, which cause molecular nitrogen and methane (the primary components of the upper atmosphere) to generate into various CHN-containing species that deposit onto the surface [2].

Despite the ubiquity of these organic minerals upon the surface, it is difficult to understand their influence on the landscape and as, in some cases, even their crystal structure is unknown let alone wider physical properties[3]. Hence we have undertaken an experimental program to address this, and are currently focusing on the missing crystal structure and physical property understanding of a number of molecular solids and co-crystals that are likely to be organic minerals upon Titan. Using a combination of neutron diffraction, X-ray diffraction and Raman scattering we have studied molecular solids including ethane, acrylonitrile, acetonitrile, butadiene and propyne, and explored what co-crystal form from the inventory of Titan’s molecules. This contribution will report highlights from these investigations.

[1] Lopes, R.M., Malaska, M.J., Schoenfeld, A.M., Solomonidou, A., Birch, S.P.D., Florence, M., Hayes, A.G., Williams, D.A., Radebaugh, J., Verlander, T. and Turtle, E.P. (2020) Nature Astronomy 4(3) pp.228-233. [2] Hörst, S. M. (2017). Journal of Geophysical Research: Planets 122 (3), 432-482 [3] Maynard-Casely, H.E., Cable, M.L., Malaska, M.J., Vu, T.H., Choukroun, M. and Hodyss, R. (2018) 103(3), pp.343-349 [4] Balzar, D. & Popa, N. C. (2004). Diffraction Analysis of the Microstructure of Materials, edited by E. J. Mittemeijer & P. Scardi, pp. 125-145. Berlin: Springer.

Over the last decade, crystal flask that converts one chemical species to another one in single-crystal-to-single-crystal (SCSC) manner has attracted much attention in crystal engineering. An important key for the construction of crystal flask is a porous space which can induce a chemical from outside of a crystal.¹ To design such a porous space, our group has intensively studied the metalloligand approach in which a pre‐prepared homometallic complex with coordination donor sites is reacted stepwise with secondary metal ions.² We established the construction of a variety of metalloarchitectures by the metalloligand approach with using thiolato groups derived from amino acids and phosphine ligands. Recently, our group has successfully prepared a microporous material of a nanometer-sized Au^ICd^II 116-nuclear cage-of-cage structure (1_CdNa) from the reaction of the tripodal-type trigold(I) metalloligand, [Au^I₃(tdme)(D-Hpen)₃] (tdme = 1,1,1-tris(diphenylphosphinomethyl)ethane, D-H₂pen = d-penicillamine), with Cd^II(NO₃)₂.³ The cage-of-cage structure was constructed from 12 building units of Au^I₆Cd^II₃ cage complex through hierarchical aggregation. Interestingly, 1_CdNa has large interstices connected by 3D channels which allow the easy incorporation and accommodation of guest molecules. Therefore, it was found that 1_CdNa underwent the stepwise SCSC transmetallation reactions to form Au^ICu^II metallocage (1_Cu). Furthermore, we found that the crystals of 1_Cu have the ability to accommodate MoO₄^2– ions (2_Mo1) and condense them to form Mo₇O₂₄^6– (2_Mo7) and β-Mo₈O₂₆^4– (2_Mo8) by the addition of protons in the solid state. These results show the availability of the large crystal interstices in 1_Cu as crystal flask, which serves as a reaction field for accommodated chemical species in crystal. Such a crystal flask reaction of polyoxomolybdate will give an important insight for not only material science but also biosynthesis in Mo-storage protein (MoSto) which contains Mo₈, Mo_5-7 and Mo₃ clusters. The detail will be discussed in the presentation.

[1] Inokuma, Y., Kawano, M. & Fujita, M. (2011). Nat. Chem. 3, 349. [2] Yoshinari, N. & Konno, T. (2016). Chem. Rec. 16, 1647. [3] Imanishi, K., Wahyudianto, B., Kojima, T., Yoshinari, N. & Konno, T. (2020). Chem. Eur. J. 26, 1827. [4] Kowalewski, B., Poppe, J., Demmer, U., Warkentin, E., Dierks, T., Ermler, U. & Schneider, K. (2012). J. Am. Chem. Soc. 134, 9768.

Stress-accumulated electrical charge to close wounds in living tissue, yet to-date this piezoelectric effect has not been realised in self-repairing synthetic materials which are typically soft amorphous materials requiring external stimuli, prolonged physical contact and long healing times (often >24h). Here we overcome many of these challenges using piezoelectric organic crystals, which upon mechanical fracture, instantly recombine without any external direction, autonomously self-healing in milliseconds with remarkable crystallographic precision (Figure 1). Atomic-resolution structural studies reveal that a 3D hydrogen bonding network, with ability to store stress, facilitates generation of stress-induced electrical charges on the fractured crystals, creating an electrostatically-driven precise recombination of the pieces via a diffusionless instant self-healing, as supported by spatially-resolved birefringence experiments. Perfect, instant self-healing creates new opportunities for deployment of molecular crystals using crystal engineering principles in robust miniaturised devices, and may also spur development of new molecular level repair mechanisms in complex biomaterials [1].

References:

[1] Bhunia S, Chandel, S., Karan, SK., Dey, S., Tiwari, A., Das, S., Kumar, N., Chowdhury, R., Mondal, S., Ghosh, I., Mondal, A., Khatua, BB., Ghosh, N., Reddy, C. M. Autonomous self-repair in piezoelectric molecular crystals. (2021) Science. 373 , 321-327

The crystalline sponge method^[1],[2] allows the absolute structural determination of non-crystalline compounds such as powder, amorphous solid, liquid, volatile matter or oily state. In this method, metal-organic frameworks (MOFs) are used as ‘crystalline sponges’ which can absorb target sample (guest) molecules from their solution into the pores and allow them to arrange themselves in a regular pattern with the help of specific interactions between MOF pores and the guests, such as π-π, CH-π, and charge-transfer interactions. This technique was first introduced in 2013^[1] and since then has grown rapidly and proved helpful in the structure elucidation of liquids and other volatile compounds.

In this work, the crystalline sponge [{(ZnI₂)₃(tris(4-pyridyl)-1,3,5- triazine)₂·x(solvent)_n] (1) was used to produce three novel encapsulation complexes of terpenes, such as geraniol-monoterpenoid, farnesol-sesquiterpenoid and β-damascone-tetraterpenoids.^[3] Along with the structure determination of the terpenoids, non-bonding CH-π, π-π interactions were identified in the host-guest complexes shown in Figure 1, which were responsible for holding the guests in the specific position with respect to the framework. Since pores of sponge 1 were hydrophobic, no hydrogen bonding between host and guest was observed.

In addition, new crystalline sponges were explored {[Co₂(bis-(3,5-dicarboxy-phenyl) terephthalamide)(H₂O)₃]·solvent_x}^[4] (2) and [Cd₇(4,4’,4’’-[1,3,5-benzenetriyltris(carbonylimino)]trisbenzoic acid)(H₂O)]·solvent _x]^[5] (3). With sponge 2 two novel inclusion complexes with 3-Phenyl-1-propanol and 2-Phenylethanol were obtained. Sponge 2 has three coordinated water molecules indicating the hydrophilic nature, which was further observed in the inclusion complexes where the hydroxyl group of guest molecules were found to form hydrogen bonds with the framework of 2. Further, 3 shows great potential to act as a crystalline sponge because of larger pore size than 1 and the hydrophilic nature which will allow a wide range of guest molecule for encapsulation and their structure elucidation.

The first developments on metal-organic frameworks, or MOFs, were made approximately four decades ago, marking the discovery of a novel class of porous materials. Initially thought to be ordered and truly crystalline, there is now an increasing realisation that defects and disorder are prevalent in MOFs, and that nontrivial arrangements can be important in physical properties [1]. Though, disorder in MOFs does not necessarily imply randomness. In fact, depending on the interactions between components, MOF structures can exhibit short-range order and long-range disorder simultaneously. This is what we refer to as correlated disorder [2]. Thorough understanding is achieved through investigation of the interactions involved in causing these states, with the aim of controlling physical properties via their manipulation.

Generally, there are three types of disorder observed in MOFs: vacancy defects, compositional disorder, and orientational/conformational disorder [3]. The latter forms the focus of this project. A key factor is the distinction between molecular point symmetry (i.e. the local structure) and that of the corresponding position in the lattice (i.e. the average structure). Namely, molecular components are arranged on a lattice of which the geometry is determined by that of the MOF, giving control over the molecular orientational degrees of freedom [4]. Since MOF geometry is often highly symmetric, lowering the symmetry of nodes and/or linkers can enable targeted design of correlated conformational disorder (Fig. 1).

In this work, correlated disorder is introduced to the highly symmetric (hypothetical) parent framework ZnO₄(BTC) (BTC = benzene tricarboxylic acid) by reducing the linker symmetry from D_3h to C_2v, giving ZnO₄(1,3-BDC) (BDC = benzene dicarboxylic acid) (Fig. 1). The resulting linker disorder is characterised via diffuse scattering observed in single crystal X-ray diffraction (SCXRD) patterns, 3DΔ-pair distribution functions (3DΔ-PDFs), and Monte Carlo code. Ultimately, we want to understand how to control defective structures in MOFs to optimise their properties, enabling utilisation in real-life applications.

[1] Bennett, T. D., Cheetham, A. K., Fuchs, A. H., Coudert, F.-X. (2017). Nat. Chem. 9, 11.[2] Keen, D. A. and Goodwin, A. L. (2015). Nat. 521, 303.[3] Meekel, E.G. and Goodwin, A.L. (2021). CrystEngComm.[4] Simonov, A. and Goodwin, A. L. (2020). Nat. Rev. Chem.

Glutathione peroxidase (GPX) [1] is a selenoenzyme containing multiple selenocysteine units in its active site. It catalyses the reduction of harmful peroxides, thus protecting cells from oxidative stress. High concentrations of active peroxides results in an alternative path of the catalytic cycle of GPX, where selenenic acid residues (R–SeOH) undergo oxidation to the corresponding seleninic (R–SeO₂H) and selenonic acids (R-SeO₃H). In general, synthetic seleninic acids and their sulfurated analogues sulfinic acids (R-SO₂H) have been reported as key component in redox regulation [2], exerting in some cases a surprising anticancer activity [3].

The reactivity of these moieties may be related to the electrophilic behaviour of selenium and, to a lesser extent, of sulphur. The propensity of an electron rich atom to act as an electrophile is related to the presence of regions of positive electrostatic potential (σ-holes) on its surface, located on the back-end of the covalent bonds formed by the considered atom. σ-hole interactions are named from the group of the periodic table to which the element behaving as an electrophile belongs; based on this, interactions given by atoms of group 16 are dubbed as Chalcogen Bonds (ChB) [4].

Here, we report the controlled oxidation of L-selenocystine (C₆H₁₂N₂O₄Se₂) in selenocysteine seleninic acid, which is a simple mimic of GPX activity. This compound was isolated and single crystals suitable for X-ray diffraction allowed to an insight at the atomic level of the electrophilic behaviour of selenium. This crystal structure suggests the possible involvement of ChB in the redox regulation activity of the seleninic acid moiety. A survey of the Cambridge Structural Database (CSD) and some computational studies on a small library of these class of compounds may confirm the propensity of seleninic (and sulfinic) acids to act as ChB donors.

The decomposition of the crystal contacts on the Hirshfeld surface between pairs of interacting chemical species enables to derive a contact enrichment ratio [1,2,3]. This descriptor yields information on the propensity of chemical species to interact with themselves and other species. The enrichment ratio is obtained by comparing the actual and equiprobable contacts. H∙∙∙N, H∙∙∙O and H∙∙∙S as well as weak H∙∙∙halogen hydrogen bonds appear generally more or less enriched, depending on the context. Larges series of molecules made of a set of chemical groups and retrieved from the Cambridge Structural Database can be investigated to find trends in the propensity of interactions to form.

The electrostatic energy of between atoms in contact was also computed using a multipolar atom model after electron density database transfer. The mean energy values of different contact types between multipolar pseudoatoms were compared statistically to the contact enrichment ratios.

The analyses suggest that hydrogen bonds are often the most enriched and attractive interactions and are therefore a driving force in the crystal packing formation for organic molecules. The methodology also enables to compare different types of hydrogen bonds which are in competition within a crystal packing. The behavior of weaker interactions such as halogen bonds is less contrasted. The methodology is a way to rank the occurrence of given synthons and the impact in crystal engineering will be discussed

The tenoxicam (4-hydroxy-2-methyl-N-2-pyridyl-2H-thieno(2,3-e)-1,2-thiazine-3-carboxamide 1,1-dioxide), is a non-steroidal anti-inflammatory drug (NSAID), member of oxicam family, widely used in the treatment of osteoporosis. Tenoxicam (TXM) could be present in the β-keto-enolic form (BKE) or β-diketone (BDK) and in a zwitterionic form (ZWC) (Figure 1). However, in solid form (more than 20 different compounds including polymorphic modifications, co-crystals, and solvates) [1 and present work] TXM has predominantly found in the zwitterionic form (ZWC). While in a dissolved form, keto-enolic equilibrium is observed since recorded by us experimental absorption and fluorescence spectra for various TXM solutions show presence two forms of TXM (called A and B) in solvents with high polarity and only A form of TNX in low polar solvents (cyclohexane, toluene, chloroform, dioxane). This led us to think about the possibility to obtain solid forms of tenoxicam contain it in BKE or BDK form.

A set of NMR measurements using various 1D- and 2D- techniques were used to assign which of TXM keto-enolic form (see Figure 1) belong to the A and B forms observed in a liquid environment. As a result, form A observed by optical methods assigns to BKE form and the form B – to ZWC. ¹H NMR spectra of tenoxicam in CDCl₃ detected at various temperatures from -55 to 25 °C show almost 100% TXM in form of BKE at 25 °C and almost 100% TXM in ZWC form at -55°C.

Taking into account optical and NMR data about the domination of BKE form in low polar solvents at room temperature, we tried to obtain solid forms of TNX containing TXM in BKE form by its crystallization from cyclohexane, toluene, dioxane, and chloroform. These experiments showed no crystal phase from cyclohexane and powder of TXM polymorph I from dioxane and toluene. Crystallization from chloroform gave single crystals of three different solvates so called TXM-CHCl₃-I (grow up at room temperature), TXM-CHCl₃-II (grow up at -18°C) and TXM-CHCl₃-III (grow up at -18°C). But in all these solvates TXM presents in ZWC form.

For understanding why TNX exists in BKE form in solution, but crystallize in ZWC form, DFT calculations in vacuo were made. It shows that BKE to be the most thermodynamically stable form, ZWC is less stable and BDK is the least stable (ΔG between BKE and these two forms of 2.20 kcal/mol and 12.49 kcal/mol, respectively). But BKE form is characterized by a large twist between A 2-pyridyl ring and TXM backbone with respect to almost flat ZWC form. Planarization of BKE form diminishes the energy difference between flatten BKE and ZWC forms almost to 0.15 kcal/mol that indicates a presence of another thin interaction within TXM molecule predisposing it to crystallization in ZWC form. This thin interaction was showed to be S-bond between thiophenil ring and carbonyl oxygen according to the analysis of intramolecular interactions within natural bond orbital theory [4]. This S-bond is significantly stronger for ZWC form as compared with flatten BKE form and it should be considered as the driving force of TXM crystallization

The authors would like to thank Dr. Anatoly A. Politov for useful discussion. SGA would like to thank Prof. Dr. Elena V. Boldyreva for her ongoing support. CT would like to thank his former supervisor Prof. Dr. Elena V. Boldyreva and his present supervisor Prof. Dr. Artem R. Oganov for their ongoing support.

SGA is indebted to Ministry of Science and Higher Education of the Russian Federation (project АААА-А19-119020890025-3).

PSS and ASK thank Ministry of Science and Higher Education of the Russian Federation for access to optical and NMR equipment (АААА-А16-116121510087-5).

Halogen bonding (XB) interactions are defined as those involving electrophilic sites (σ-holes) associated to a covalently bonded atom of group-17 with nucleophilic sites from either the same or a different molecule¹. These σ-hole regions are expected to exhibit along the extension of covalent bonds and can be finely tuned by the electronic nature of substituents in the molecule bearing the halogen atom.

In a previous study involving donor-acceptor complexes, we have succeeded to co-crystallize iodine substituted imide derivatives with pyridine derivatives. In these systems, we have pointed out a strong halogen bonding motif where the halogen atom is significantly shifted towards the acceptor moiety. For one of them, which is leading to an ionic crystal rather than a co-crystal², an electrostatic secondary interaction of C=O^δ-···I ^δ+ type has been discussed as one of the reasons behind such a halogen atom shift towards the acceptor. In our work, we are actually investigating the evolution of such XB interactions in an organic binary adduct composed of N-Iodosaccharin and Pyridine (NISac.Py) via X-ray diffraction experiments under pressure. These experiments were undertaken with a Membrane Diamond Anvil Cell (MDAC) under external pressure ranging from 0 GPa to 4.5 GPa, by using an in-house set-up (with the in-situ measurement of pressure from time to time) developed in our laboratory and adapted to the diffractometer (Bruker D8 venture) that was used to collect high-pressure X-ray diffraction data.

Aiming to analyse the influence of the molecular environment on the XB motif of NISac.Py, X-ray diffraction studies have permitted to follow the evolving behaviour of the N_sac-I···N’_py interactions as a function of pressure, which results in the shifting of the halogen atom position between donor and acceptor moieties. This trend might be linked to a potential change of state from co-crystal to ionic crystal form under pressure. The study also opens up an opportunity to understand the modification of secondary interactions as a function of pressure. Another interesting finding resulting from this work is the occurrence of a mechanical twinning and its behaviour as a function of pressure, which is analysed in detail. Periodic theoretical calculations were also carried out by applying isotropic external pressures. They were followed by the analyses of the Equation of State (EOS), molecular environments and non-covalent interactions, all of them showing good agreements with experimental results. In summary, this work illustrates the possibility of working with pressure as another thermodynamic variable that permits to alter weak intermolecular interactions and therefore to explore phase transformation or polymorphic phases in other donor-acceptor systems formed by similar interactions.

[1] Cavallo, G., Metrangolo, P., Milani, R., Pilati, T., Priimagi, A., Resnati, G. & Terraneo, G. (2016). Chem. Rev. 116, 2478–2601. [2] Makhotkina, O., Lieffrig, J., Jeannin, O., Fourmigué, M., Aubert, E. & Espinosa, E. (2015). Cryst. Growth Des. 15, 3464–3473.

Keywords: High-pressure X-ray diffraction; Membrane Diamond Anvil Cells; Halogen bonding; Mechanical Twinning

V.V.S. thanks the French ANR and the Region Grand-Est for a PhD fellowship. We thank PMD²X X-ray diffraction facility of the Institut Jean Barriol, Université de Lorraine, for X-ray diffraction measurements and ERDF for funding high-pressure experimental set-up. High-performance computing resources were partially provided by the EXPLOR center hosted by Université de Lorraine

Controlling supramolecular synthetic output, with the aim to achieve targeted macroscopic properties, is the main goal of crystal engineering.[1] Mechanical flexibility, as one of the highly desired properties of functional materials, has recently become a feature of a growing number of crystalline compounds.[2-5] Plastic deformation, together with elastic response, is frequently observed among organic molecular crystals,[3] but quite rarely noticed among crystalline metal-organic compounds.[4,5] Since the introduction of metal cations to organic systems allow us to achieve specific properties such as magnetic and electric ones, and therefore opens a wide range of possible applications, it is clear that there is a need for determining structural requirements that need to be fulfilled to equip metal-organic crystals with mechanical flexibility.Recently, it was shown that cadmium(II) coordination polymers equipped with halopyrazine ligands adaptably respond to applied external stimuli, displaying elastic flexibility.[5] It was observed that introducing a slight structural changes, simply by exchanging bridging halide anion or halogen atom on halopyrazine ligand, changes the extent of elastic response significantly, while the quantification of their mechanical behaviour clearly showed that they can be categorized into three main subgroups, highly, moderately and slightly elastic. To get an invaluable insight into the phenomenon, we decided to systematically examine similar classes of coordination polymers by introducing slight structural differences through the exchange of supramolecular functionalities only. Herein we opted for pyridine-based ligands decorated with cyano functionality to explore their impact on macroscopic mechanical output. It was determined that the position of cyano group on pyridine ring, as well as used bridging halide anion, dictate the nature and extent of mechanical response. For crystals that displayed elastic behaviour, the responses were quantified and correlated with structural features, primarily the strength and geometry of supramolecular interactions, and compared with the mechanical behaviour of similar metal-containing systems.

[1] Desiraju, G. R. (2007) Angew. Chem. Int. Ed. 46, 8342.

[2] Commins, P., Tilahun Desta, I., Prasad Karothu, D., Panda, M. K., Naumov, P. (2016) Chem. Commun. 52, 13941.

[3] Saha, S., Mishra, M. K., Reddy, C. M., Desiraju, G. R. (2017) Acc. Chem. Res. 51, 2957.

[4] Worthy, A., Grosjean, A., Pfrunder, M. C., Xu, Y., Yan, C., Edwards, G., Clegg, J. K., McMurtrie, J. C. (2018) Nat. Chem. 10, 65.

[5] Đaković, M., Borovina, M., Pisačić, M., Aakeröy, C. B., Soldin, Ž., Kukovec, B.-M., Kodrin, I. (2018) Angew. Chem. Int. Ed. 57, 14801.

This work has been fully supported by Croatian Science Foundation under the project IP-2019-04-1242.

Strong intermolecular interactions serve as vital tools in cocrystal assembly. Halogen bonding (XB) [1], a highly directional interaction, is most often observed between a halogen-atom donor and electron-rich acceptors, such as oxygen or nitrogen. However, XBs can also be used for the organization of arenes in the solid state through interactions with aromatic p-systems, as previously explored in the dichroic and pleochroic cocrystals of naphthalene or azulene, respectively. [2]

This presentation will outline our study of XB cocrystal structures containing various polycyclic aromatic hydrocarbons (PAHs), and evaluate the reliability of halogen bonding to carbon as an overlooked tool for crystal engineering.

[1] Christopherson, J. C.; Topić, F.; Barrett, C. J.; Friščić, T. (2018). Crystal Growth & Design, 18, 1245-1259.

[2] Vainauskas, J.; Topić, F.; Bushuyev, O. S.; Barrett, C. J.; Friščić, T. (2020) Chemical Communications 56, 15145-15148.