XXV General Assembly and Congress of the
International Union of Crystallography - IUCr 2021
August 14 - 22, 2021 | Prague, Czech Republic
Conference Agenda
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Session Overview |
Session | ||
MS-6: Application of electron crystallography to functional materials
Invited: Mauro Gemmi (Italy), Maria Roslova (Germany) | ||
Session Abstract | ||
In the nano-era, electron crystallography is sometimes the only possible tool for structure characterization. Thus, characterization of properties of functional materials cannot be done without application of these methods. Issues such as study of structural changes at atomic scale occurring in functional materials will be covered at this MS. For all abstracts of the session as prepared for Acta Crystallographica see PDF in Introduction, or individual abstracts below. | ||
Introduction | ||
Presentations | ||
10:20am - 10:25am
Introduction to session 10:25am - 10:55am
3D electron diffraction on nanoparticles with a complex structure. 1Center for Nanotechnology Innovation@NEST, Istituto Italiano di Tecnologia, Pisa, Italy; 2Department of Nanochemistry, Istituto Italiano di Tecnologia, Genova, Italy The synthesis of inorganic compounds in form of nanoparticles of few nanometers has opened a new world for chemistry, with the discovery of unexpected properties and also of entirely new crystal structures. At the beginning, simple stoichiometries related with crystal structures of low complexity have been mainly explored. As far as nanochemistry grew searching for exotic properties, the exploration has extended towards more complex phase diagrams, where the complexity of the crystal structure is a real challenge. In these cases, the crystallographer is hampered by the limited crystal size that enlarges the powder x-ray diffraction peaks and quite often cannot rely on the knowledge of the bulk structure, which can be different from the nanocrystalline form or even not stable in the same conditions. Conversely, 3D electron diffraction (3D ED) has demonstrated its potential for solving crystallographic problems where the size of the crystal grains was the limiting factor [1]. A 3D ED single crystal diffraction experiment is performed with a beam that can be as small as few hundreds of nanometers, and the collected 3D intensity data sets are suitable for structure solution [2]. We report here the application of 3D ED to extreme cases, where the size of the crystalline grains was smaller or in the range of 100 nm and the powder x-ray diffraction was not able to give a definite answer. The challenge is to establish which is the minimum crystal size that we can investigate in this way. All the nanoparticles we analysed have unknown and not trivial crystal structures. As first example we report the crystal structure of Cu2-xTe, a not stoichiometric plasmonic nanocrystal that exhibits a complex 1x3x4 super-structure of a pseudo-cubic basic cell, due to the ordering of copper vacancies. The pseudosymmetry of the underlying basic structure induces a strong twinning and therefore data on single individuals could be taken only from grains smaller than 150nm. 3D ED allowed the determination of the super-structure with the identification of 27 Te and 32 Cu in the asymmetric unit and the location of copper vacancies [3]. A second example is the perovskite-related structure of Cs3Cu4In2Cl13 nanocrystals. This crystal structure was synthesized with the aim to obtain a double perovskite of composition Cs2CuInCl6, isostructural to Cs2AgInCl6. 3D ED on nanoparticles of 100 nm revealed that the obtained structure is instead a vacancy ordered perovskite, A2BX6, in which 25% of the A sites are occupied by [Cu4Cl]3+ clusters and the remaining 75% by Cs+, while the B sites are occupied by In3+ ions. Interestingly, while a Rietveld refinement on powder x-ray data results in a crystal structure where Cs+ and [Cu4Cl]3+ are disordered on 8 equivalent sites, 3D ED shows that they exists nanoparticles where [Cu4Cl]3+ clusters and Cs+ are ordered on different sites, lowering the symmetry from cubic Fm-3m to cubic Pn-3m [4]. The last example is the crystal structure determination of Pb4S3Br2, a compound never reported in bulk that we synthesised in form of nanoparticles. 3D ED revealed that this compound is isostructural with the high pressure phase of Pb4S3I2 and attested that the colloidal synthesis is able to freeze a high pressure metastable phase in form of nanoparticles. 3D also revealed that once the size of the nanoparticles has increased above a certain size (> 50nm) and their shape has changed from spherical to elongated platelets, the structure relaxes with the longest cell parameter that increase from 14.6 to 15.5 Å [5]. In this last case we have reached our minimum crystal size, being able to reconstruct the 3D reciprocal space of a 50 nm nanoparticle. The examples reported demonstrate that 3D ED is a powerful tool for exploring the crystal structure of not trivial nanoparticles and we expect that, with the use of smaller parallel beam and a dedicated set up, this limit can be pushed further to investigate the crystal structure of nanoparticles in the 10 nm range. [1] Gemmi, M., Mugnaioli, E., Gorelik, T.E., Kolb, U., Palatinus, L., Boullay, P., Hovmöller, S., Abrahams, J.P. (2019). ACS Cent. Sci. 5, 1315. [2] Gemmi, M., Lanza, A. (2019). Acta Crystallogr. B75, 495. [3] Muganioli, E., Gemmi, M., Tu, R., David, J., Bertoni, G., Gaspari, R., De Trizio, L., Manna, L. (2018). Inorg. Chem. 57,10241. [4] Kaiukov, R.,Almeida, G., Marras, S., Dang, D., Baranov, D., Petralanda, U., Infante, I., Mugnaioli, E., Griesi, A., De Trizio, L., Gemmi, M., Manna, L. (2020). Inorg. Chem. 59, 548. [5] Toso, S., Akkerman, Q. A., Martín-García, B., Prato, M., Zito, J., Infante, I., Dang, Z., Moliterni, A., Giannini, C., Bladt, E., Lobato, I., Ramade, J., Bals, S., Buha, J., Spirito, D., Mugnaioli, E., Gemmi, M., Manna L. (2020). J. Am. Chem. Soc. 142, 10198. 10:55am - 11:25am
Reliable structure determination of K-intercalated RuCl3 nanoflakes by 3D electron crystallography and multivariate analysis of fused EELS and EDX spectrum images 1Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden; 2Department of Physics, Technische Universität Dresden, Germany; 3Institute for Solid State and Materials Research (IFW) Dresden, Germany; 4Institute of Physics, University of Amsterdam, The Netherlands 2D nanosheets are intensely researched as new quantum materials and components of next-generation electronic and spintronic devices with unprecedented magnetic, transport and optical properties. In particular, the thickness-dependency of structural and physical properties is subject of close scrutiny. α-RuCl3 is a spin ½ honeycomb material that exhibits exotic magnetic ground states both in bulk1 and exfoliated2 forms. Its flakes and intercalates feature high environmental stability and retain the in‐plane honeycomb structure during wet-chemistry functionalization2. RuCl3 nanosheets are a robust test-bed for fabrication of new nanocomposites in both acidic or basic aqueous solutions, and their performance as electrodes for electrochemical reduction/ion transfer reactions can be further optimized. Reliable structural and compositional characterization during downscaling and intercalation is one of the goals that will enable well-controlled nanosheet functionalization. We synthesized K-intercalated RuCl3 by electrochemistry in an aqueous KCl solution. Conventional X-ray diffraction methods fail to characterize such intercalates due to the presence of multiple nm-sized domains, stacking faults and other defects associated with the layered morphology. Instead, we for the first time determine the local structure and capture the essential properties on the nm-length scale by collecting the multimodal 3DED–STEM–EELS–EDX data. The 3DED method is one of the very few that provides both in-plane and out-of-plane structural information, which is indispensable for layered materials. The K0.5RuCl3 layered intercalate (sp. gr. P-31m) is stacked differently than the α-RuCl3 parent compound (sp.gr. C2/m): the K atoms in the interlayer space are coordinated by six equivalent Cl atoms to form the [KCl6] octahedra that share corners with the six equivalent [RuCl6] octahedra. As a hallmark of STEM, EELS, and EDX spectroscopy, spatial mapping techniques were used to trace local changes in the chemical composition. A multimodal data fusion3 helped to overcome the severe spectral overlap and high sparseness of EDX data. The retrieved abundance profiles revealed spatially resolved phases with differing in the K:Ru:Cl ratio, the Ru oxidation state and in the oxygen content. This microinhomogeneity is a rather local disorder, which might cause only minor local symmetry changes, and could be associated with concomitant water molecules co-intercalating into the α-RuCl3 matrix together with the K+ cations. Figure 1. a,b Reconstructed 3D reciprocal lattice of the K-doped α-RuCl3, scale bar is 4 nm-1, c In-plane and out-of-plane structure of K0.5RuCl3 found by 3DED, d TEM overview image, e,f Abundance maps from fused EDX and EELS data. Scale bar is 200 nm. [1] Roslova, M., Hunger, J., Bastien, G., Pohl, D., Haghighi, H. M., Wolter, A. U. B., Isaeva, A., et al. (2019). Inorg. Chem. 10, 6659-6668; Bastien, G., Roslova, M., Haghighi, M. H., Mehlawat, K., Hunger, J., Isaeva, A., et al. (2019). Phys. Rev. B. 99, 214410. [2] Weber, D., Schoop, L. M., Duppel, V., Lippmann, J. M., Nuss, J., Lotsch, B. V. (2016). Nano Lett. 16(6), 3578–3584. [3] Thersleff, T., Budnyk, S., Drangai, L., Slabon, A. (2020). Ultramicroscopy. 219, 113116; Thersleff, T., Jenei, I. Z., Budnyk, S., Dörr, N., Slabon, A. (2021). ACS Appl. Nano Mater. 4 (1), 220–228. 11:25am - 11:50am
3D-ΔPDF from electron diffraction data 1Inorganic Chemistry, University of Oxford, United Kingdom; 2Department of Structural Analysis, Institute of Physics of the CAS, Prague, Czechia; 3Institute of Inorganic Chemistry of the Leibniz University Hannover, Germany; 4Kristallographie und Strukturphysik, Friedrich-Alexander-Universität, Erlangen, Germany Many functional materials seem to have surprisingly simple average structures with some disordered components. To understand the relationship between the structure of a material and its complex physical properties, a full description including local order is necessary. Hence, the diffuse scattering has to be analysed. The recently established three-dimensional delta pair distribution function (3D-ΔPDF) maps local deviations from the average structure and allows a straightforward interpretation of local ordering mechanisms [1]. Many functional materials can only be grown as powders. While powder X-ray and neutron diffraction experiments can give limited insight into disordered structural arrangements, electron diffraction techniques allow to capture large portions of reciprocal space even for nanocrystals. Here, we demonstrate how the 3D-ΔPDF can be used with electron diffraction to understand the complete local structure of the ion conductor calcium stabilized zirconia (Zr0.82Y0.18O1.91). Zr0.82Y0.18O1.91 crystallizes in the fluorite structure and shows composition disorder on both the metal and oxygen site. Due to the vastly different bond lengths of Y-O and Zr-O, strongly structured diffuse scattering is observed alongside the Bragg reflections (see Figure (a)). By employing the 3D-ΔPDF to electron diffraction data, we can directly interpret the local correlations (see Figure (b)). Large single crystals of Zr0.82Y0.18O1.91 that are also suitable for X-ray and neutron measurements were investigated. By comparing the results from our electron ΔPDF to X-ray and neutron ΔPDFs we demonstrate the reliability of the 3D-ΔePDF. To our knowledge, this is the first 3D-ΔePDF ever reported and this proof of principle is an important step towards the full description of a disorder model. This has important implications for the large variety of disordered materials of which single crystals for X-ray or neutron techniques are not available. In those cases, the 3D-ΔePDF will pave the way to understanding and tailoring physical properties. Figure 1. (a) hk0 reciprocal space section with diffuse scattering and Bragg reflections. (b) 3D-ΔePDF in the ab0.25 layer showing the relaxation of metal oxygen bond distances around (0.25,0.25,0.25). [1] Weber, T., & Simonov, A. (2012). Z. Kristallogr., 227(5), 238-247. 11:50am - 12:15pm
Electron diffraction for the promotion of stable and green metal-organic frameworks 1Stockholm University, Stockholm, Sweden; 2IMDEA Energy, Madrid, Spain; 3Universidad Nacional Autónoma de México, Mexico City, Mexico Metal-organic frameworks (MOFs) are a class of nanoporous materials that have developed into one of the most widely studied research fields in chemistry of the past two decades. Single crystal X-ray diffraction still remains as the preferred method for structure determination, but the technique requires sufficiently large crystals. Traditionally and still predominantly to this day, MOFs are prepared using synthesis conditions that are optimized for producing larger single crystals, which includes dissolving starting materials with polar organic solvents, such as DMF or methanol, followed by heating under solvothermal conditions. With the emergence of fast electron diffraction (ED) techniques such as 3D ED or MicroED, solving crystal structures from small nano-sized crystals has never been easier for crystals with organic constituents that traditionally were considered too beam sensitive for transmission electron microscopy. This provides the opportunity to easily study MOFs that can only be synthesized as small nanocrystals. Many of the more stable MOFs have a tendency to form as smaller crystallites, which can now be conveniently studied by ED. In addition this also makes it easier to study MOFs made using less typical synthesis conditions which may be less hazardous, more environmentally friendly and require less energy input. Access to fast ED has allowed us to easily focus on the development of new stable MOFs prepared under green and ambient synthesis conditions. SU-101 was prepared using nonhazardous and edible starting materials which were stirred in water at room temperature without any other energy input.[1] The reaction starts and ends as a suspension in water, nonetheless the starting materials are fully converted into the MOF. Scaling up the synthesis of SU-101 is easily achieved as the MOF forms at room temperature and ambient pressure in water. For the first time in a MOF, ellagic acid was used as the organic linker. Ellagic acid is common in many plants and is one of the building units of naturally occurring polyphenols known as tannins. It is well known as an antioxidant and is common in fruits, berries, nuts, and wine. Unlike most MOF linker molecules, ellagic acid does not contain carboxylic acids groups but instead has multiple phenol groups which can chelate to metal cations forming strong bonds and hence robust framework structures. SU-101 demonstrates excellent stability in organic solvents and water even at elevated temperatures, simulated physiological media, and also in a wide pH range (2-14). In addition to demonstrating good stability, SU-101 exhibits promising behavior in the capture of hazardous sulfur containing gases, and demonstrated one of the highest uptake capacities for hydrogen sulfide among MOFs. Due to the stable structure, the lack of heating during synthesis and the use of a poor solvent (water), SU-101 was synthesized as small nanocrystals. The crystal structure of SU-101 was solved by ED with relative ease. The advent of fast ED techniques and the relative ease now in solving structures of nanocrystals containing organic components, has changed our habits in the chemistry laboratory regarding the synthesis of novel crystalline materials. Rather than by default using organic solvents, elevated temperatures and pressures, we now focus on using greener reagents and ambient synthesis conditions directly from the early stages in the development of novel biocompatible and stable MOFs. 12:15pm - 12:40pm
Crystal structure of the Al78Mn17.5Pt4.5 phase as revealed by electron crystallography 1Ben Gurion University of the Negev, Beer Sheva, Israel; 2MaTecK GmbH, 52428 Jülich, Germany; 3Peter-Grünberg-Institut, Forschungszentrum Jülich, 52425 Jülich, Germany Structure of high temperature “Al3Mn” (T) phase was investigated numerously. Studies of binary and ternary extensions of T-phase resulted in many published atomic models [1-8]. Until today, exact space group and atomic positions of transition metals in this structure is a matter of dispute. In current research, atomic model of the Al78Mn17.5Pt4.5 phase (quenched from 800 °C) was successfully derived using a combination of electron crystallography methods. This structure was regarded as ternary extension of the “Al3Mn” T–phase. The lattice parameters of the Al78Mn17.5Pt4.5 T-phase were found to be a = 14.720(4) Å, b = 12.628(2) Å, c = 12.545(3) Å (as refined against X-ray diffraction data). Using convergent beam electron diffraction (CBED), the space group of this ternary composition was proved to be non-centrosymmetric Pna21, instead of Pnam - which describes the symmetry of the binary T-phase. Atomic model was determined applying direct methods, utilized in SIR2011 [9], on electron diffraction tomography data and refined using ShelXL [10]. At the Al78Mn17.5Pt4.5 composition, the Pt atoms were not distributed randomly in the Mn/Al sublattices, but adopted two specific Wyckoff sites, therefore, thiscomposition should be regarded as an ordered variant of the T-structure. On the other hand, CBED study of the T-phase samples with a bit different stoichiometry (Al71.3Mn25.1Pt3.6) allowed attribution of their structure to the original T-phase structure type, i.e. centrosymmetric. Using Barnighausen tree [11], these two structures (centrosymmetric and non-centrosymmetric) were found to be related. References:
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