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The solid phases of deuterium sulphide by powder neutron diffraction

Published/Copyright: August 25, 2010
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Abstract

Powder neutron diffraction studies confirm that D2S has 3 solid-state phases at ambient pressure. Phases I and II are cubic and orientationally disordered with space groups Fm[unk]m (a = 5.8486(8) Å at 160 K) and Pa[unk] (a = 5.7647(6) Å at 120 K), respectively. The deuterium scattering density arising from the disorder is modelled using symmetry-adapted spherical harmonic functions, which show a reduction from “twelve-fold” to “six-fold” disorder on cooling from phase I to phase II. For the fully ordered low-temperature phase III, a new structure has been determined which bears little resemblance to that reported in a previous neutron diffraction study. The structure is orthorhombic, space group Pbcm, with a = 4.0760(1) Å, b = 13.3801(5) Å and c = 6.7215(3) A at 1.5 K. The structure is essentially hexagonally close-packed, with distortions to accommodate the hydrogen atoms. The structure is antiferroelectric with the alignment of the molecular dipoles along the a direction.

Published Online: 2010-08-25
Published in Print: 1990

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