Structural stabilities, mechanical and thermodynamic properties of chalcogenide perovskite ABS3 (A = Li, Na, K, Rb, Cs; B = Si, Ge, Sn) from first-principles study

In this study, first-principles calculations have been used to study the mechanical and thermodynamic properties of chalcogenide perovskite ABS(3) (A = Li, Na, K, Rb, Cs; B = Si, Ge, Sn) in the triclinic phase. The structural stabilities of perovskite were investigated through Goldschmidt's tolerance factor (t) and phonon dispersion. It was indicated that all of the investigated materials construct stable perovskite structures. The mechanical properties of chalcogenide perovskites ABS(3) were systematically investigated by density functional theory (DFT). The DFT method was considered within the meta-generalized gradient approximation revTPSS. The elastic properties of materials give the data necessary in understanding the bonding property between adjacent atomic planes, stiffness, bonding anisotropic, and structural stability of the material. The independent elastic constants C-ij have been used for the prediction of mechanical properties like bulk modulus (B), Shear modulus (G), Young's modulus (E) Poisson's ratio (nu), and the universal anisotropic index (A(U)). The mechanical stability, brittleness, and ductility behaviors of materials were discussed. The covalent, ionic, and metallic nature of the materials were also discussed. The thermodynamic parameters including heat capacity, entropy, enthalpy, and free energy were also computed and discussed with a wide range of temperatures (0-1000 K).