Structural and vibrational properties of methane up to 71 GPa

Article

关键词: DIAMOND-ANVIL CELL;    X-RAY-DIFFRACTION;    SOLID METHANE;    HIGH-PRESSURE;    HYDROCARBONS;    SYSTEM;   

DOI  :  10.1103/PhysRevB.104.184105

来源: SCIE

【 摘 要 】

Single-crystal synchrotron x-ray diffraction, Raman spectroscopy, and first principles calculations have been used to identify the structure of the high-pressure (HP) phase of molecular methane above 20 GPa up to 71 GPa at room temperature. The structure of the HP phase is trigonal R3, which can be represented as a distortion of the cubic phase B, previously documented at 7-15 GPa and confirmed here. The positions of hydrogen atoms in the HP phase have been obtained from first principles calculations, which also demonstrated the stability of this structure above 260 K at 25 GPa. The molecules occupy four different crystallographic sites in phase B and 11 sites in the HP phase, which result in splitting of molecular stretching modes detected in Raman spectroscopy and assigned here based on a good agreement with the Raman spectra calculated from the first principles. Our study points out to a single HP phase unlike up to three HP phases proposed previously based on the Raman spectroscopy results only.

【 授权许可】

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