First-principles study of structural, elastic, electronic and thermodynamic properties of topological insulator Sb2Te3 under pressure

Abstract

The structural, elastic, electronic and thermodynamic properties of the rhombohedral topological insulator Sb2Te3 (α-Sb2Te3) are investigated by the generalized gradient approximation (GGA) with the PBESOL exchange–correlation functional in the framework of density-functional theory. The calculated lattice parameters of Sb2Te3 at the ground state are in good agreement with the available experimental data and better than other calculated results. The pressure dependence of the elastic constants Cij, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson’s ratio σ of Sb2Te3 are also obtained successfully. The obtained density of states, charge density difference and total charge density show that Sb–Te bonds have some covalent features at the ground state. Finally, we investigate the shear sound velocity VS, longitudinal sound velocity VL, and Debye temperature ΘE from our elastic constants of Sb2Te3, as well as the thermodynamic properties from quasi-harmonic Debye model. We obtain that the heat capacity Cv and the thermal expansion coefficient α of Sb2Te3 at 0GPa and 300K are 120.79Jmol−1K−1 and 5.19×10−5K−1, respectively.