NMR studies of diffusion anisotropy in metal hydride single crystals

Abstract We report on a theoretical and experimental study of hydrogen diffusion in single crystals of α-ScH 0.25 and β-V 2 H which was concerned with the anisotropy of the NMR relaxation rate R 1 . In α-ScH 0.25 we find appreciable anisotropy at low temperature associated with local one-dimensional motion; theory and experiment agree fairly well on both the magnitude and the angular dependence of the anisotropy. In β-V 2 H the calculations made use of jump times obtained from neutron scattering. In this case again experiment and theory agree on shape; here experiment gives a larger magnitude.