A neutron scattering study of the vibrational and diffusional motions of deuterium in the α and β phases of VD .5

Abstract

The quasi-elastic and inelastic scattering of cold neutrons ( E 0 = 5 meV) from VD .5 in the α and β phases have been measured. In agreement with earlier results for vanadium hydrides, the broadening due to diffusion in the β phase is too small to be measured. In the α phase, the diffusive broadening in the quasi-elastic region compared to vanadium hydride is consistent with the ratio of the square root of the masses of the two isotopes. The local mode frequencies observed for both the α and β phases are also consistent with a square root of mass dependence, compared to earlier results for vanadium hydride. The observed similarities show that, for this concentration, the hydride and deuteride of vanadium are analogous, in spite of known differences in the phase diagrams for the two isotopes.