Pressure effect on the structural, elastic, electronic and optical properties of the Zintl phase KAsSn, first principles study

In this work, a first-principles study of ternary Zintl phase KAsSn compound using density-functional theory (DFT) method within the generalized gradient approximation developed by Wu-Cohen (GGA-Wc) has been performed. Based on the optimized structural parameter, the electronic structure, elastic and optical properties have been investigated. The calculated lattice constants agree reasonably with the previous results. The effect of high pressure on the structural parameters has been shown. The elastic constants were calculated and satisfy the stability conditions for hexagonal crystal. These indicate that this compound is stable in the studied pressure regime. The single crystal elastic constants (Cij) and related properties are calculated using the static finite strain technique, moreover the polycrystalline elastic moduli such as bulk modulus, shear modulus, micro-hardness parameter Hν, Young's modulus and Poisson's ratio were estimated using Voigt, Reuss and Hill's (VRH) approximations. The elastic anisotropy of the KAsSn was also analyzed. On another hand the Debye temperature was obtained from the average sound velocity. Electronic properties have been studied throughout the calculation of band structure, density of states and charge densities. It is shown that this crystal belongs to the semiconductors with a pseudo gap of about 0.34 eV. Furthermore, in order to clarify the optical transitions of this compound, linear optical functions including the complex dielectric function, refractive index, extinction coefficient, optical reflectivity, absorption coefficient and loss function were performed and discussed.