Phase transition, dynamical and electronic properties of BeO: First-principles investigations

The phase transition, dynamical and electronic properties of BeO have been investigated by first-principles calculations based on the density functional theory (DFT). The calculated phonon dispersion curves of hexagonal wurtzite (B4) phase BeO agree well with the experimental data. Under compression, the phonon dispersion curves of B4 phase BeO do not show any anomaly or instability. At zero pressure, the phonon frequencies of rocksalt (B1) phase BeO around the Γ point become imaginary, signaling a structural instability. Within the quasiharmonic approximation, the B4–B1 phase boundary under high pressures and high temperatures has been obtained. Comparing the Gibbs free energy differences between B4 phase and zinc blende (B3) phase, we have predicted the B3 phase BeO is instability in our applied range of pressures and temperatures. The electronic structure calculated results show that the B4 phase BeO transforms from direct gap to indirect gap semiconductor with the increasing pressure. The B4 phase BeO becomes more covalence under high pressure from the Mulliken analysis.