The crystal structure of methane B at 8 GPa-An alpha-Mn arrangement of molecules

H. E. Maynard-Casely*, L. F. Lundegaard, I. Loa, M. I. McMahon, E. Gregoryanz, R. J. Nelmes, J. S. Loveday

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

From a combination of powder and single-crystal synchrotron x-ray diffraction data we have determined the carbon substructure of phase B of methane at a pressure of similar to 8 GPa. We find this substructure to be cubic with space group I (4) over bar 3m and 58 molecules in the unit cell. The unit cell has a lattice parameter a = 11.911(1) angstrom at 8.3(2) GPa, which is a factor of root 2 larger than had previously been proposed by Umemoto et al. [J. Phys.: Condens. Matter 14, 10675 (2002)]. The substructure as now solved is not related to any close-packed arrangement, contrary to previous proposals. Surprisingly, the arrangement of the carbon atoms is isostructural with that of a-manganese at ambient conditions. (C) 2014 AIP Publishing LLC.

Original languageEnglish
Article number234313
Number of pages7
JournalThe Journal of Chemical Physics
Volume141
Issue number23
DOIs
Publication statusPublished - 21 Dec 2014

Keywords

  • X-RAY-DIFFRACTION
  • HIGH-PRESSURE
  • SOLID METHANE
  • SINGLE-CRYSTAL
  • ROOM-TEMPERATURE
  • DISSOCIATION
  • VOYAGER-2
  • INTERIORS
  • MANGANESE
  • CH4

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