The vibrational spectrum of magnesium hydride from inelastic neutron scattering and density functional theory

Light-weight magnesium metal can reversibly store up to 7wt.% hydrogen and is therefore interesting for application as hydrogen storage material. Neutron vibrational spectroscopy has been used to study the interactions of hydrogen atoms with it surroundings. The neutron spectra are compared directly with density functional theory calculations providing detailed insight in structure and dynamics. Dispersion of the vibrational modes has to be taken into account in order to reproduce the data. This study on bulk magnesium hydride will provide a bench mark for similar studies on nanostructured magnesium alloys: these are more promising as hydrogen storage materials because of their significantly faster hydrogen sorption processes. Because of its sensitivity and the compatibility to calculations, the vibrational spectra of these nanostructured compounds can be used as a probe for the local structure and the influence of the nanostructure on the potential landscape experienced by the hydrogen. Parameters can be extracted for MD and Monte Carlo calculations of slower diffusion processes.