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Title: The crystal structure of methane B at 8 GPa—An α-Mn arrangement of molecules

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 ∼8 GPa. We find this substructure to be cubic with space group I4{sup ¯}3m and 58 molecules in the unit cell. The unit cell has a lattice parameter a = 11.911(1) Å at 8.3(2) GPa, which is a factor of √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 α-manganese at ambient conditions.
Authors:
; ; ; ; ; ;  [1]
  1. SUPA, School of Physics and Astronomy and Centre for Science at Extreme Conditions, The University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom)
Publication Date:
OSTI Identifier:
22413342
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 23; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CARBON; CRYSTAL STRUCTURE; LATTICE PARAMETERS; MANGANESE; METHANE; MOLECULES; MONOCRYSTALS; POWDERS; PROPOSALS; SPACE GROUPS; SYNCHROTRONS; X-RAY DIFFRACTION