Ab Initio Study of Structural, Electronic, Elastic, Mechanical, and Optical Properties of K4XP2 (X = Zn, Cd) Compounds for Optoelectronic Applications

Abstract

The structural electronic, elastic, mechanical and optical properties of the ternary compounds K4ZnP2 and K4CdP2 have been studied by means of density functional theory (DFT) using the plane waves method. The generalized gradient approximation with the Perdew-Burke-Ernzerhof (GGA-PBE) functional has been used as the exchange correlation. The study has shown that the compounds are thermodynamically and mechanically stable at zero pressure, making them suitable for synthesis and application for industrial use. In addition, the studied compounds have been found to be semiconducting with indirect band gaps of 1.068 eV and 0.947 eV for K4ZnP2 and K4CdP2, respectively. The refractive indices have been calculated to be 2.20 and 2.23 for K4ZnP2 and K4CdP2, respectively. The absorption coefficient of K4ZnP2 and K4CdP2 has been found to cover the UV-Vis regions of the electromagnetic spectrum; hence the compounds are good UV-Vis light absorbers and may therefore find potential in photovoltaic applications. The electronic states formation of valence band has been found to be due to contribution of P 3p and Zn 4p states in K4ZnP2, while in K4CdP2 is due to P 3p and Cd 5p, on the other hand the conduction band is due to contribution of the unoccupied Zn 4p and Cd 5p states in both compounds, respectively.