Pressure-induced phase transitions of lanthanide monoarsenides LaAs and LuAs with a NaCl-type structure |
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Authors: | I Shirotani K YamanashiJ Hayashi N IshimatsuO Shimomura T Kikegawa |
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Institution: | a Faculty of Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho Hokkaido, Muroran-shi 050-8585, Japan b SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyougo 679-5198, Japan c IMSS, KEK, 1-1 Oho, Tsukuba-shi, Ibaraki 305-0801, Japan |
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Abstract: | By use of synchrotron radiation the powder X-ray diffraction of lanthanide monoarsenides LaAs and LuAs with a NaCl-type structure has been studied up to 60 GPa at room temperature. First-order phase transitions with the crystallographic change were found at around 20 GPa for LaAs, and 57 GPa for LuAs. The high-pressure form of LaAs is a tetragonal structure and can be viewed as a distorted CsCl-type structure. The atoms in the tetragonal structure are located at La: 0, 0, 0; As: 1/2, 1/2, 1/2. The space group is P4/mmm. The structural change to the tetragonal structure occurs with the volume collapse of about 10%. The structure of these high-pressure phases of LuAs is unknown. The volume vs. pressure curves for LaAs and LuAs are fitted by a Birch equation of state. The bulk moduli of both arsenides are 92±6 GPa for LaAs and 85±3 GPa for LuAs. The high-pressure structural behavior of LaX (X=P, As and Sb) and LnAs (Ln=lanthanide) with the NaCl-type structure is discussed. |
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Keywords: | 61 10 Nz 61 66 Fn |
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