Browsing by Author "Loa, I"

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    The crystal structure of methane B at 8 GPa—an α-Mn arrangement of molecules
    (AIP Scitation, 2014-12-18) Maynard-Casely, HE; Lundegaard, LF; Loa, I; McMahon, MI; Gregoryanz, E; Nelmes, RJ; Loveday, JS
    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 ¯ 3m I4¯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. Matter14, 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. © 2014, AIP Publishing LLC.