Neutron diffraction study of the deuterides of the over-stoichiometric compounds LaNi5+x

The deuterides of three intermetallic compounds LaNi5+x with x=0, 0.2 and 0.4 have been prepared and analyzed by neutron powder diffraction at two different deuterium concentrations. On one hand, the crystallographic properties of the α and the β phases have been studied with the two phases in equilibrium on the pressure plateau characteristic for the phase transition. On the other hand, the β phase has been studied as a single phase in the solid solution domain. Crystal structures were refined using the Rietveld method. Crystal symmetry, lattice parameters and deuterium sites and occupancy parameters are reported for all the different phases. Anisotropic line profile analysis has been used to characterize the strains induced by deuterium absorption in the various regions of the Pressure-Composition-Isotherm curves. Results are compared for the different values of x and related to the cycle life properties for each compound