Theoretical investigation of the vibrational properties of BeH2 and Li2 BeH4

First-principles calculations of BeH2 and Li2 BeH4 were performed and compared to inelastic neutron scattering. The crystal structure (P 21 /c space group) of Li2 BeH4 contains BeH4 tetrahedral units similar to those in α -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 bondings in Li2 BeH4 and provide a better understanding of the nature of the bonding in these materials.