Ab initio calculation of the elastic properties and the lattice dynamics of the AlAs x Sb1−x alloy under pressure

Abstract

The lattice dynamics and the elastic properties of the ternary AlAs x Sb1−x alloy have been studied using the density-functional perturbation theory within the local density approximation and employing the virtual-crystal approximation. We study the variation of the optical phonon frequencies (ωTO and ωLO), the high-frequency (ϵ∞) and static (ϵ0) dielectric coefficients, the dynamic effective charge (Z*) and the elastic constants (C 11, C 12, C 44) as a function of the composition (x) and the pressure. We have also predicted the behavior of the optical and acoustical phonons with composition x at the X and L high symmetry points under pressure and determined the Grüneisen parameter. We have found that no mechanical instabilities are associated with the structural transition at high pressures for all compositions.