Pressure effects on structural and elastic properties of BeO from first-principles calculations

Abstract

The structural, elastic, and thermodynamic properties of B4-phase BeO under high pressure have been investigated with the density functional theory. BeO is stable in the B4 phase up to 117.87 GPa, and then transforms directly into the B1 phase. The phonon-dispersion curves of B4-phase BeO show dynamical stability under high pressure. The calculated elastic constants are in excellent agreement with the experiments. The high-pressure elastic constant indicates that B4-phase BeO is mechanically stable with the applied pressure. The pressure dependences of the bulk modulus B, shear modulus G, and Young's modulus E, the compression wave velocity VP, the bulk wave velocity VB, and the shear wave velocity VS of B4-phase BeO are all successfully obtained. The sound velocities along different directions of B4-phase BeO under high pressure are obtained. Moreover, the azimuthal anisotropy of the compression and shear aggregate wave velocities for different pressures are predicted for the first time. Within the quasiharmonic approximation, the pressure and temperature dependences of the thermodynamic properties including the thermal expansion coefficient, heat capacity and entropy are predicted.