The high-entropy alloys/medium-entropy alloys（HEA/MEA）have a great deal of attention, since they have exceptional mechanical properties. In order to clarify the mechanism, we investigated the local structure in the prototype equiatomic alloy CrCoNi by the measurement of the extended x-ray absorption fine structure. The structural disorder is larger in the Cr sites than those in other constituent elements, which is consistent with the larger atomic displacement of the Cr atoms predicted by the first-principles calculations. The Cr atom has a solute-type characteristic in the 3d transition metal atoms that enhances the local disorder. If the sample is annealed in the intermediate temperature range, the difference in the local disorder among the constituent elements decreases.

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We propose a new method to extract the informations of microscopic structure from the extended X-ray absorption fine structure by the application of sparse modeling based on a simplified single-scattering approximation of photo-electron waves. This method can extract the sparse radial distribution function of the atoms located nearby the target atom and can estimate the Debye-Waller factor without any assumption of the micro-structures. Therefore, this method is expected to exhibit considerable ability in the crystallographic researches on new materials and such cooperative researches of data-driven science and crystallographic measurements are strongly expected to extend the frontiers in various research fields.

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スパースモデリングの一種であるLASSO法により、広域X線吸収微細構造 (EXAFS)の3次モーメントχk^3の基底関数分解を行った。EXAFSは光電子波干渉により、原子の近距離構造が解明できる強力な測定法である。本研究では、LASSOの正則化パラメータλと

・σの最適化を、クロスバリデーションエラーを規範として行った。この方法をCu結晶に適用し、動径分布関数と一致する結果を得た。

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The Debye-Waller factors and resonances in the diffraction of the atomic and molecular beams from solid surfaces are described.
The Debye temperatures determined by means of molecular beams are always larger than those obtained from LEED. These results are discussed qualitatively on the basis of the facts that the properties of the interactions of atoms and molecules with solid surfaces are considerably different from those of the interactions with solid surfaces.
The anomalous behavior of the diffraction intensities, which is called a resonance, has been found for many systems of molecules-solid surfaces. The intensity profiles in resonance are explained from the viewpoint of the standard scattering theory. Also it is emphasized that the interaction potentials of molecules with solid surfaces are determined by analysing only the resonance positions in the observed intensity curves.

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It is well known that Ge (100) surface shows reconstructed structure like Si (100) surface. This surface formed structure which has asymmetric dimers in the topmost layer at low temperature, and the order-disorder phase transition occurs at 200 K, the structure change to structure. For Ge (100) surface X-ray diffraction measurements and the structure analysis are performed by R. Rossmann, et al. However, they use the isotropic Debye-Waller factor.
In actuality, Ge dimers makes flip-flop motion at particular direction. We try to perform the structure analysis of Ge (100) surface using the results of the first-principles calculation and the anisotropic Debye-Waller factor. Obtained results show improvement compared with previous analysis.

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An investigation has been made on the local structure and the gel to crystalline conversion mechanism in BaTiO₃ monolithic gels derived from hydrolysis of concentrated Ba, Ti alkoxide precursor solutions with a Ba/Ti molar ratio of 1.00 during aging at 30°C by means of XRD, Ba L_III-edge EXAFS, Ti K-edge XANES, and ICP. The results indicate that local structures of amorphous monolithic gels obtained immediately after gelation consisted of Ba-TiO₆ clusters coordinated with alkoxyl or hydroxyl ligands as a structural unit, which underwent condensation polymerization by corner-sharing of TiO₆ octahedra to form a three-dimensional gel-network. The conversion of gel to crystalline barium titanate nano-particles during aging at 30°C can be explained by a model that the crystalline phase directly forms from the amorphous phase without dissolution, deposition and diffusion of the reactant species nor generation of intermediate phases.

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　本研究では, 低速電子線回折法(LEED)を用いてイリジウム(Ir)(111)清浄表面及び一酸化窒素(NO)吸着表面の二つの試料について, スポット強度の温度依存性の解析と動力学的解析によってデバイ温度を評価した．LEEDスポット強度の温度依存性を用いた解析ではIr (111)清浄表面におけるデバイ温度は250～280K, NO吸着表面におけるデバイ温度は220～235K程度であることが分かった．また動力学的解析結果からはIr (111)清浄表面におけるデバイ温度は310K, バルクのデバイ温度が440 Kとなり, 表面ではバルクよりも低い値となることが分かった．表面でのデバイ温度が低いことは表面原子の振動振幅がバルク内部に比べて大きいことを示しており, さらに表面にNOが吸着することによりさらに増大すると考えられる．［本要旨はPDFには含まれない］

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