The isotypism of BeH2 and SiO2: an ab initio study

Polymorphs of BeH2 isotypical to SiO2 framework structures have been investigated by density functional theory calculations using a plane wave basis set in conjunction with ultra-soft pseudo-potentials. All calculated structures turned out to be stable with respect to small atomic displacements and are therefore possible metastable BeH2 modifications. The most stable modification at ambient pressure is the already known Ibam structure. We predict a phase transition to a high pressure modification. Linear response calculations have been performed to investigate the connection between the nature of bonding and the lattice dynamics of several BeH2 polymorphs.