Study of optical, electronic and structural properties of ZINTL phase KAsSn

Abstract

The thesis has been the subject of theoretical study on the structural and physic al properties of compound Zintl phase KAsSn. The structural, electronic, elastic and optical properties of KAsSn compound have been investigated by employing first principles method using the density-functional theory (DFT) method within the generalized gradient approximation developed by Wu-Cohen (GGA-Wc). The equilibrium geometries of the studied materials have been optimized at 0 K for different pressure values between 0 and 20 GPa by using the CASTEP package. The calculated lattice constants are in good agreement with experiments with a deviation less than 0.87%, 1.63% and 0.06% for a, c and V respectively. 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, were estimated using Voigt, Reuss and Hill’s (VRH) approximations. 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 0.34eV. 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. The direct band gap and high absorption power in the ultraviolet energy range show the effective use of this compound in the optoelectronic devices.