Over the past decade, advances in electron diffraction (ED) have significantly improved the determination and refinement of crystal structures, making it a viable alternative to traditional X-ray diffraction (XRD), especially for very small volumes, such as nanoparticles (NPs). This work evaluates the application of advanced 3D ED techniques to the analysis of isolated NPs, focusing on their efficacy and limitations in terms of crystal size and accuracy of results. Our investigation begins by addressing the challenges of obtaining 3D ED data for NPs, including sample preparation, instrument capabilities, and the choice of 3D ED methods. We find that 3D ED can provide highly accurate structure refinements for crystals in the 50-100 nm range and is also effective for the analysis of NPs as small as 10 nm. While kinematical approximations often provide accurate refinements similar to those obtained from powder XRD, the accuracy depends on the specific data set and may not always align with traditional reliability indicators. Our study shows that dynamical scattering effects, even in tiny crystals, challenge the assumption that they are negligible in thin crystal scenarios. Addressing these effects through full dynamical refinement significantly improves the accuracy and reliability of the structure determination. This report suggests a paradigm shift in viewing dynamic scattering effects not as mere obstacles but as opportunities to explore crystal structures in greater detail on smaller scales. By embracing these complexities, 3D ED can provide precise and reliable structural insights that are critical to the advancement of nanotechnology and materials science.

• Klíčová slova
• crystallography, dynamical refinement, electron diffraction, electron microscopy, oxide nanoparticles,
• Publikační typ
• časopisecké články MeSH

A new platinate was recently discovered when Nd2O3 was explored as a platinum capture material in the Ostwald process, formed by a direct reaction between gaseous PtO2 and Nd2O3. The crystal structure of this new platinate and its composition, Nd10.67Pt4O24, are here reported for the first time. The compound is synthesized either by a direct reaction between PtO2(g) and Nd2O3 or by the citric acid chemical route. Based on 3-dimensional electron diffraction data and Rietveld refinement of high-resolution synchrotron and neutron powder diffraction data, we describe its crystal structure in space group I41/a. The compound is structurally related to the Ln11-x Sr x Ir4O24 (Ln = La, Pr, Nd, and Sm) phases with a double perovskite (A2BB'O6)-like crystal structure with A-site cation deficiency. Owing to the fixed oxidation state of Pt(IV), two of the four Nd sites are partly occupied to provide charge neutrality, with Nd4 taking a split position. On heating, Nd10.67Pt4O24 decomposes into Nd2O3 and Pt. A plateau in the thermogravimetric curves measured in 33 vol % O2 in N2 indicates the presence of an intermediate Pt(II) phase at around 960 °C, probably isostructural with La4PtO7.

• Publikační typ
• časopisecké články MeSH

Conventional refinement strategies used for three-dimensional electron diffraction (3D ED) data disregard the bonding effects between the atoms in a molecule by assuming a pure spherical model called the Independent Atom model (IAM) and may lead to an inaccurate or biased structure. Here we show that it is possible to perform a refinement going beyond the IAM with electron diffraction data. We perform kappa refinement which models charge transfers between atoms while assuming a spherical model. We demonstrate the procedure by analysing five inorganic samples; quartz, natrolite, borane, lutecium aluminium garnet, and caesium lead bromide. Implementation of kappa refinement improved the structure model obtained over conventional IAM refinements and provided information on the ionisation of atoms. The results were validated against periodic DFT calculations. The work presents an extension of the conventional refinement of 3D ED data for a more accurate structure model which enables charge density information to be extracted.

• Publikační typ
• časopisecké články MeSH

Recent advances in 3D electron diffraction (3D ED) have succeeded in matching the capabilities of single-crystal X-ray diffraction (SCXRD), while requiring only submicron crystals for successful structural investigations. One of the many diverse areas to benefit from the 3D ED structural analysis is main-group chemistry, where compounds are often poorly crystalline or single-crystal growth is challenging. A facile method for loading and transferring highly air-sensitive and strongly oxidizing samples at low temperatures to a transmission electron microscope (TEM) for 3D ED analysis was successfully developed and tested on xenon(II) compounds from the XeF2-MnF4 system. The crystal structures determined on nanometer-sized crystallites by dynamical refinement of the 3D ED data are in complete agreement with the results obtained by SCXRD on micrometer-sized crystals and by periodic density-functional theory (DFT) calculations, demonstrating the applicability of this approach for structural studies of noble-gas compounds and highly reactive species in general. The compounds 3XeF2·2MnF4, XeF2·MnF4, and XeF2·2MnF4 are rare examples of structurally fully characterized xenon difluoride-metal tetrafluoride adducts and thus advance our knowledge of the diverse structural chemistry of these systems, which also includes the hitherto poorly characterized first noble-gas compound, "XePtF6".

• Publikační typ
• časopisecké články MeSH

X-ray and electron diffraction methods independently identify the S-enantiomer of Berkecoumarin [systematic name: (S)-8-hydroxy-3-(2-hydroxypropyl)-6-methoxy-2H-chromen-2-one]. Isolated from Berkeley Pit Lake Penicillium sp., Berkecoumarin is a natural product with a light-atom composition (C13H14O5) that challenges in-house absolute structure determination by anomalous scattering. This study further demonstrates the utility of dynamical refinement of electron-diffraction data for absolute structure determination.

• Klíčová slova
• Berkecoumarin, absolute structure determination, chromenone, coumarin, crystal structure, dynamical refinement, electron diffraction, microED, natural product,
• Publikační typ
• časopisecké články MeSH

Dynamical refinement is a well established method for refining crystal structures against 3D electron diffraction (ED) data and its benefits have been discussed in the literature [Palatinus, Petříček & Corrêa, (2015). Acta Cryst. A71, 235-244; Palatinus, Corrêa et al. (2015). Acta Cryst. B71, 740-751]. However, until now, dynamical refinements have only been conducted using the independent atom model (IAM). Recent research has shown that a more accurate description can be achieved by applying the transferable aspherical atom model (TAAM), but this has been limited only to kinematical refinements [Gruza et al. (2020). Acta Cryst. A76, 92-109; Jha et al. (2021). J. Appl. Cryst. 54, 1234-1243]. In this study, we combine dynamical refinement with TAAM for the crystal structure of 1-methyluracil, using data from precession ED. Our results show that this approach improves the residual Fourier electrostatic potential and refinement figures of merit. Furthermore, it leads to systematic changes in the atomic displacement parameters of all atoms and the positions of hydrogen atoms. We found that the refinement results are sensitive to the parameters used in the TAAM modelling process. Though our results show that TAAM offers superior performance compared with IAM in all cases, they also show that TAAM parameters obtained by periodic DFT calculations on the refined structure are superior to the TAAM parameters from the UBDB/MATTS database. It appears that multipolar parameters transferred from the database may not be sufficiently accurate to provide a satisfactory description of all details of the electrostatic potential probed by the 3D ED experiment.

• Klíčová slova
• 3D electron diffraction, dynamical refinement, electron crystallography, microcrystal electron diffraction, multipolar scattering factors, quantum crystallography, transferable aspherical atom model,
• Publikační typ
• časopisecké články MeSH

Our study compares short-range order parameters refined from the diffuse scattering in single-crystal X-ray and single-crystal electron diffraction data. Nb0.84CoSb was chosen as a reference material. The correlations between neighbouring vacancies and the displacements of Sb and Co atoms were refined from the diffuse scattering using a Monte Carlo refinement in DISCUS. The difference between the Sb and Co displacements refined from the diffuse scattering and the Sb and Co displacements refined from the Bragg reflections in single-crystal X-ray diffraction data is 0.012 (7) Å for the refinement on diffuse scattering in single-crystal X-ray diffraction data and 0.03 (2) Å for the refinement on the diffuse scattering in single-crystal electron diffraction data. As electron diffraction requires much smaller crystals than X-ray diffraction, this opens up the possibility of refining short-range order parameters in many technologically relevant materials for which no crystals large enough for single-crystal X-ray diffraction are available.

• Klíčová slova
• 3D difference pair distribution functions, 3D electron diffraction, 3D-ΔPDF, 3DED, single-crystal diffuse scattering,
• Publikační typ
• časopisecké články MeSH

Estimating the error in the merged reflection intensities requires a full understanding of all the possible sources of error arising from the measurements. Most diffraction-spot integration methods focus mainly on errors arising from counting statistics for the estimation of uncertainties associated with the reflection intensities. This treatment may be incomplete and partly inadequate. In an attempt to fully understand and identify all the contributions to these errors, three methods are examined for the correction of estimated errors of reflection intensities in electron diffraction data. For a direct comparison, the three methods are applied to a set of organic and inorganic test cases. It is demonstrated that applying the corrections of a specific model that include terms dependent on the original uncertainty and the largest intensity of the symmetry-related reflections improves the overall structure quality of the given data set and improves the final Rall factor. This error model is implemented in the data reduction software PETS2.

• Klíčová slova
• data reduction, electron diffraction, error analysis, error modelling,
• Publikační typ
• časopisecké články MeSH

Continuous-rotation 3D electron diffraction methods are increasingly popular for the structure analysis of very small organic molecular crystals and crystalline inorganic materials. Dynamical diffraction effects cause non-linear deviations from kinematical intensities that present issues in structure analysis. Here, a method for structure analysis of continuous-rotation 3D electron diffraction data is presented that takes multiple scattering effects into account. Dynamical and kinematical refinements of 12 compounds-ranging from small organic compounds to metal-organic frameworks to inorganic materials-are compared, for which the new approach yields significantly improved models in terms of accuracy and reliability with up to fourfold reduction of the noise level in difference Fourier maps. The intrinsic sensitivity of dynamical diffraction to the absolute structure is also used to assign the handedness of 58 crystals of 9 different chiral compounds, showing that 3D electron diffraction is a reliable tool for the routine determination of absolute structures.

• Publikační typ
• časopisecké články MeSH

Zeolites are key materials in both basic research and industrial applications. However, their synthesis is neither diverse nor applicable to labile frameworks because classical procedures require harsh hydrothermal conditions, whereas post-synthesis methods are limited to a few suitable parent materials. Remaining frameworks can fail due to amorphization, dissolution, and other decomposition processes. Nevertheless, stopping degradation at intermediate structures could yield new zeolites. Here, by optimizing the design and synthesis parameters of the parent zeolite IWV, we "caught" a new, highly crystalline, and siliceous zeolite during its degradation. IWV seed-assisted crystallization followed by gentle transformation into the water-alcohol system yielded the highly crystalline daughter zeolite IPC-20, whose structure was solved by precession-assisted three-dimensional electron diffraction. Without additional requirements, as in conventional (direct or post-synthesis) strategies, our approach may be applied to any chemically labile material with a staged structure.

• Publikační typ
• časopisecké články MeSH