Theoretical investigation of the vibrational properties of BeH2 and Li2BeH4...

First-principles calculations of BeH2 and Li2BeH4 were performed and compared to inelastic neutron scattering. The crystal structure (P21/c space group) of Li2BeH4 contains BeH4 tetrahedral units similar to those in alpha-BeH2 (Ibam space group), but separated from each other by Li atoms. Calculated vibrational density of states revealed the origin of the observed major vibrational modes. Charge density maps and electronic density of states indicate interplay between covalent and ionic bonding in Li2BeH4 and provide a better understanding of the nature of the bonding in these materials.