Phase transition, electronic, elastic and thermodynamic properties of Bi2Te3 under high pressure

To understand the Bi-Te substitutional alloys, the structural, electronic and elastic properties of Bi2Te3 with І, II, III and ІV phases under high pressure have been calculated, using the first principle method based on density functional theory. Specifically, some basic physical parameters, e.g., lattice constants, bulk modulus, elastic constants, shear modulus, Young's modulus and Poison's ratio, are predicted. There exist four structural phase transitions, corresponding to І → II: 8.2 GPa, II → III: 13.4 GPa and III → ІV: 14.0 GPa which are in perfect agreement with the experimental data. The obtained structural parameters and electronic bands at various pressures agree well with the experimental and theoretical values. According to the calculated elastic constants, we obtain the mechanical stability, ductile or brittle characters, elastic stiffness and elastic anisotropy of Bi2Te3 with four phases. In the frame works of quasi-harmonic Debye model, the temperature and pressure variations of the Debye temperature, heat capacity and thermal expansion coefficient are discussed in the wide ranges.