The structure and dynamics of hydrogen in LaNi5H6studied by elastic and inelastic neutron scattering

Abstract
The structure of LaNi5D6 has been studied by powder neutron diffraction. It is described in space group P31m with the deuterium atoms distributed over one fully and one partly occupied interstitial site. The dynamics of hydrogen in LaNi5H6 at temperatures of 293, 390, 440 and 493K have been studied by cold neutron scattering experiments. According to these the H atoms showed a high local mobility on the partly occupied H site. Assuming a simple diffusive behaviour with circular symmetry for this localised part of the motion, relaxation times of the order of 10-10 s were obtained at 293K. This indicates H atom jumps about 100 times faster than observed for other types of diffusive motion in the structure. The activation energy for the former was rather low, about 75 meV.