Ab initio calculation of lattice dynamics in BeO

Ground state lattice vibrational properties of wurtzite-BeO are reported using an ab initio plane-wave pseudopotential method. The ab initio results for the phonon dispersion relations are in good agreement with the available experimental data. The only discrepancy observed between experiment and present data for the longitudinal optic frequency at the centre of the Brillouin zone for a displacement along the symmetry axis is expected to be due to the indirect measurement of that mode in the experiment. The dielectric constant, the Born effective charges and the elastic constants for the compound are computed from the lattice dynamics. All of them agree well with the experimental results. The elastic constants calculated using the phonon spectra agree reasonably well with the results from other first-principles calculations. The good agreement of the quantities calculated, with the experimental results pave the way for future studies on the contribution of lattice vibrations to the pressure-induced phase transition in this compound. We try to understand the features of the phonon spectra from the component-projected phonon densities of states and by analysing the contributions of each atom type towards each normal mode. We find that the phonon spectra of BeO contains features common to some of the members with the same crystal structure as well as to some of the members in the same alkaline earth oxide group.