Electronic Structure of Ge-Sb-Te System Calculated by DV-Xα Method

Abstract

Germanium-antimony-tellurium (Ge-Sb-Te) system comprised the GeSb2Te4, GeSb4Te7, and Ge2Sb2Te5 compounds which are the most widely used materials with electronic structure of narrow band gap energy. In this work, we studied electronic structure of Ge-Sb-Te system by using the discrete variational (DV)-Xα molecular orbital method based on the self-consistent Hartree-Fock-Slater model in order to investigate thermoelectric materials. The calculation was designed based on Ge13Sb20Te52, Ge7Sb12Te40, and Ge14Sb6Te26 model cluster atoms which performed to GeSb2Te4, Ge2Sb2Te5, and GeSb4Te7 compounds with the symmetry (9Cv) in order to convert radial function for molecular orbitals of model cluster atoms. The findings were the electronic structure comprising the model cluster atoms, energy level, density of state, bond overlap population and electron density at wave function number of HOMO and LUMO showed narrow energy gap of 0.022 eV, 0.016 eV and 0.037 eV of Ge13Sb26Te52, Ge7Sb12Te40, and Ge14Sb6Te26, respectively. The narrow energy gap was relevant to improving the thermoelectric performance of Ge-Sb-Te system.