DFT study of structural, elastic properties and thermodynamic parameters of Bi₂S₃ under hydrostatic pressures

The pressure dependencies of structural properties, stability, mechanical properties, mechanical anisotropic, linear compressibility, Debye temperature, minimum thermal conductivity and thermal expansion coefficient of the orthorhombic Bi₂S₃ in the Pnma structure have been investigated using density functional theory. All calculated properties are in excellent agreement with experimental results, which imply the reliability of the present calculation method. The obtained elastic constants satisfying that the Bi₂S₃ crystals are mechanically stable up to 9.18 GPa and its hardness is improved under compression. The surface constructions and planar contours of bulk and Young's moduli at (1 0 0), (0 1 0) and (0 0 1) crystal planes indicate that bulk modulus is more isotropic than Young's modulus, and anisotropies in both moduli decrease under compression. Furthermore sound velocity, Debye temperature and minimum thermal conductivity are found to be increasing with pressure. The thermal expansion coefficient of Bi₂S₃ has a strong pressure dependence and its thermal conductivities are extraordinary low which demonstrate its technological application as novel thermal barrier coating materials. Unfortunately, there is currently no experimental measurements of elastic constants and other related properties for comparison.