ORCID Profile
0000-0001-5865-6449
Current Organisation
University of Tsukuba
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Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0DT02795B
Abstract: A range of experimental techniques is used to quantify how disorder varies with synthesis conditions in spinel ZnAl 2 O 4 .
Publisher: International Union of Crystallography (IUCr)
Date: 24-11-2017
DOI: 10.1107/S2052520617014044
Abstract: A multi-temperature structural study of Mg 2 Si and Mg 2 Sn was carried out from 100 to 700 K using synchrotron X-ray powder diffraction. The temperature dependence of the lattice parameters can be expressed as a = 6.3272 (4) + 6.5 (2) × 10 −5 T + 4.0 (3) × 10 −8 T 2 Å and a = 6.7323 (7) + 8.5 (4) × 10 −5 T + 3.8 (5) × 10 −8 T 2 Å for Mg 2 Si and Mg 2 Sn, respectively. The atomic displacement parameters (ADPs) are reported and analysed using a Debye model for the averaged U iso giving Debye temperatures of 425 (2) K for Mg 2 Si and 243 (2) K for Mg 2 Sn. The ADPs are considerably smaller for Mg 2 Si than for Mg 2 Sn reflecting the weaker chemical bonding in the Mg 2 Sn structure. Following the heating, an annealing effect is observed on the lattice parameters and peak widths in both structures, presumably due to changes in the crystal defects, but the lattice thermal expansion is almost unchanged by the annealing. This work provides accurate structural parameters which are of importance for studies of Mg 2 Si, Mg 2 Sn and their solid solutions.
Publisher: International Union of Crystallography (IUCr)
Date: 27-07-2017
Publisher: Springer Science and Business Media LLC
Date: 12-02-2018
DOI: 10.1038/S41563-017-0012-2
Abstract: Van der Waals (vdW) solids have attracted great attention ever since the discovery of graphene, with the essential feature being the weak chemical bonding across the vdW gap. The nature of these weak interactions is decisive for many extraordinary properties, but it is a strong challenge for current theory to accurately model long-range electron correlations. Here we use synchrotron X-ray diffraction data to precisely determine the electron density in the archetypal vdW solid, TiS
Publisher: Wiley
Date: 06-10-2023
Publisher: International Union of Crystallography (IUCr)
Date: 2023
DOI: 10.1107/S2052252522011782
Abstract: Serial femtosecond crystallography for small-unit-cell systems has so far seen very limited application despite obvious scientific possibilities. This is because reliable data reduction has not been available for these challenging systems. In particular, important intensity corrections such as the partiality correction critically rely on accurate determination of the crystal orientation, which is complicated by the low number of diffraction spots for small-unit-cell crystals. A data reduction pipeline capable of fully automated handling of all steps of data reduction from spot harvesting to merged structure factors has been developed. The pipeline utilizes sparse indexing based on known unit-cell parameters, seed-skewness integration, intensity corrections including an overlap-based combined Ewald sphere width and partiality correction, and a dynamically adjusted post-refinement routine. Using the pipeline, data measured on the compound K 4 [Pt 2 (P 2 O 5 H 2 ) 4 ]·2H 2 O have been successfully reduced and used to solve the structure to an R 1 factor of ∼9.1%. It is expected that the pipeline will open up the field of small-unit-cell serial femtosecond crystallography experiments and allow investigations into, for ex le, excited states and reaction intermediate chemistry.
Publisher: International Union of Crystallography (IUCr)
Date: 27-07-2017
DOI: 10.1107/S2052520617006357
Abstract: In recent years powder X-ray diffraction has proven to be a valuable alternative to single-crystal X-ray diffraction for determining electron-density distributions in high-symmetry inorganic materials, including subtle deformation in the core electron density. This was made possible by performing diffraction measurements in vacuum using high-energy X-rays at a synchrotron-radiation facility. Here we present a new version of our custom-built in-vacuum powder diffractometer with the s le-to-detector distance increased by a factor of four. In practice this is found to give a reduction in instrumental peak broadening by approximately a factor of three and a large improvement in signal-to-background ratio compared to the previous instrument. Structure factors of silicon at room temperature are extracted using a combined multipole–Rietveld procedure and compared with ab initio calculations and the results from the previous diffractometer. Despite some remaining issues regarding peak asymmetry, the new diffractometer yields structure factors of comparable accuracy to the previous diffractometer at low angles and improved accuracy at high angles. The high quality of the structure factors is further assessed by modelling of core electron deformation with results in good agreement with previous investigations.
No related grants have been discovered for Hidetaka Kasai.