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Structural and vibrational properties of methane up to 71 GPa

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Bykov, M 
Bykova, E 
Pickard, CJ 
Martinez-Canales, M 
Glazyrin, K 

Abstract

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. The structure of 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 HP phase have been obtained from first principles calculations. The molecules occupy four different crystallographic sites in phases B and eleven 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.

Description

Keywords

51 Physical Sciences, 34 Chemical Sciences, 3406 Physical Chemistry

Journal Title

Physical Review B

Conference Name

Journal ISSN

2469-9950
2469-9969

Volume Title

Publisher

American Physical Society (APS)
Sponsorship
Engineering and Physical Sciences Research Council (EP/P022596/1)