AB INITIO CALCULATION OF THE LATTICE DYNAMICS OF THE ZnSe1-xTex ALLOY

Abstract

The lattice dynamics of the ternary ZnSe 1-x Te x alloy have been studied using first-principles calculations. These are done using the density-functional perturbation theory (DFPT) within the local density approximation (LDA) and employing the virtual-crystal approximation (VCA). We study the variation of the optical phonon frequencies (ω TO and ω LO ), the high-frequency dielectric coefficient (ε∞) and the dynamic effective charge (Z*) as a function of the composition (x). We found that the ω TO and ω LO follow a quadratic law in x and agree well with the experiment which proves that the VCA is a reliable method for mixed modes determination (2 bonds-1 mode). The obtained ε∞ and Z* have a quadratic form with x. We have also predicted the behavior of the optical and acoustical phonons with x at the high symmetry point X and L.