Ab initio study of structural, electronic and optical properties of ternary chalcopyrite semiconductors

In this paper, structural, electrical and optical properties of AgGaX2 (X=S, Se, Te) were studied by using Full Potential Linear Augmented Plane Wave (FP-LAPW) based on density functional theory. Perdew Becke Ernzerhof (GGA-PBE) and Wu Cohen Generalized gradient approximation (GGA-Wc), Engel Voskov Generalized Gradient Approximation (EV) and modified Becke-Johnson exchange potential (MBJ) were used for the exchange correlation potential. GGA-PBE was closed to the other and experimental data for lattice constant, bulk modulus (B) and its first derivative (B′), and MBJ potential was in good agreement with the experiment and other calculations for band gap energy and the optical properties. Band structure, total and partial density of states were plotted to obtain electronic properties and the band gap was direct for all components. By using imaginary and real part of dielectric functions, some optical properties such as reflection coefficient (R), refractive index (n), extinction coefficient (k) were obtained and the role of X atoms (X=S, Se, Te) in optical properties were investigated.