Hydrogen dynamics in heavy alkali metal hydrides obtained through inelastic neutron scattering

Inelastic neutron scattering spectra from polycrystalline NaH, KH, RbH and CsH, measured at low temperature in the energy transfer range 3 meV < E < 500 meV, are reported. From the medium-energy regions, coinciding with the optical phonon bands, accurate hydrogen-projected densities of phonon states are extracted and compared to ab initio lattice dynamics results. The overall agreement is very good. Further lattice dynamics calculations, based on a pairwise Born–Mayer semi-empirical potential scheme, were also performed, providing only limited and qualitative agreement with the experimental data. In conclusion, incoherent inelastic neutron spectroscopy proves to be a stringent validation tool for lattice dynamics simulations of H-containing materials.Fil: Auffermann, G.. Max Planck Institut fur Chemische Physik fester Stoffe; AlemaniaFil: Barrera, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Química; ArgentinaFil: Colognesi, D.. Istituto di Fisica Applicata ‘Nello Carrara’. Consiglio Nazionale delle Ricerche; ItaliaFil: Corradi, G.. Istituto di Fisica Applicata ‘Nello Carrara’. Consiglio Nazionale delle Ricerche; ItaliaFil: Ramirez Cuesta, A. J.. Rutherford Appleton Laboratory; Reino UnidoFil: Zoppi, M.. Istituto di Fisica Applicata ‘Nello Carrara’. Consiglio Nazionale delle Ricerche; Itali