Theoretical Investigations On Elastic, Thermal And Lattice Dynamic Properties Of Chalcopyrite Znsnx2 (X = P, As, Sb) Under Pressure And Temperature: The First-Principles Calculation

We performed the first-principles calculations on the elastic and thermal properties for chalcopyrite ZnSnX2 (X = P, As, Sb), employing the ultrasoft pseudo-potentials and generalized gradient approximation (GGA) under the frame of density functional theory. The equilibrium structural lattice constants are in good agreement with reported data. The elastic characteristics were evaluated under high-pressure condition (0-20 GPa), such as the elastic constants, bulk modulus, shear modulus, Poisson's ratio, Zener anisotropy and compressibility index. Combining with quasi-harmonic Debye model, the thermal properties were confirmed at different temperatures (0-1200 K) and pressures (0-20 GPa), including the heat capacity, thermal expansion, Debye temperature, entropy, and Gruneisen parameter. Based on the semi-empirical relation, the hardness of materials was determined at various temperatures and pressures. Finally, the phonon spectrum curves and vibration frequencies of phonon were evaluated to confirm the thermodynamic stability of ZnSnX2. The Raman scattering spectrum and infrared absorption spectrum were simulated for chalcopyrite ZnSnX2.