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The crystal structures and phase transition of methyl bromide

1986; Taylor & Francis; Volume: 57; Issue: 5 Linguagem: Inglês

10.1080/00268978600100661

1362-3028

P. Gerlach, B. H. Torrie, B. M. Powell,

Crystallography and molecular interactions

The detailed crystal structures of deuterated methyl bromide in both its α-and β-phases have been determined at 175 K and 146 K respectively by neutron powder profile measurements. The α-phase has space group Cmc21 while the β-phase has space group Pnma and both have a quasi-two-dimensional character. The major characteristic of the first order transition is a large change in the relative orientation of the two molecules lying in the mirror planes. The transition is successfully interpreted in terms of changes in the topology of the lattice energy surface calculated as a function of temperature from pair-wise interatomic potentials.