First-principles study of structural, dynamical, elastic, electronic, optical, and thermodynamic properties of Na2ZnSnS4 compound

Abstract

The structural, dynamical, elastic, electronic, optical, and thermodynamic properties for the Na2ZnSnS4 compound is reported using the density functional theory in the framework of the full-potential linearized augmented plane wave method within the Wu and Cohen generalized gradient and Tran–Blaha modified Becke–Johnson approaches. Calculations shows that Na2ZnSnS4 is more stable in the kesterite phase. Phonon studies indicate that this compound is dynamically stable. The elastic constants are calculated and used to confirm the mechanical stability. Moreover, our compound is thermodynamically stable and the conditions of Sn-rich/Na-poor are necessary to form a single-phase Na2ZnSnS4 crystal. The shear modulus, Young’s modulus, Poisson’s ratio, anisotropy factor, Lamé’s constant, and Pugh indicator have also been calculated. The electronic properties shows that Na2ZnSnS4 has a direct gap (Γ–Γ) of 3.18 eV. The optical properties suggests that Na2ZnSnS4 is a good candidate for nonlinear optical applications. The thermodynamic properties such as Debye temperature, thermal expansion coefficient, heat capacities, and entropy are also estimated under temperature and pressure effects.