First-principles WC-GGA and mBJ calculations for structural, electronic, optical and elastic properties of MxGa1-xSb (M=Al, In, B) ternary alloys

Abstract

GaSb based ternary alloys have indicated wide range variations in physical, electronic and optical properties. In the present study the structural, electronic, optical and elastic properties of MxGa1-xSb (M = Al, In, B) ternary alloys have been reported and discoursed based on the first-principles investigation. The current work attempts to provide an insight into the evolution of electronic, optical and elastic properties of ternary alloys of MxGa1-xSb (M = Al, In, B) with variation in their constituent compounds. Density functional theory (DFT) operation based on the augmented plane wave + local orbitals (APW + lo) method has been employed to estimate the structure, density of states (DOS), bandstructure, optical and the elastic properties of ternary alloys MxGa1-xSb (M = Al, In, B) for (x = 0, 0.25, 0.50, 0.75, 1) compositions. Computations were performed using the exchange-correlation energy functional from Wu-Cohen, a generalized-gradient approximation (WC-GGA) as well as the original modified Becke-Johnson exchange potential (mBJ) available with the WIEN2k code. As WC-GGA has been observed to underestimate the bandgap, the bandstructure of ternary alloys MxGa1-xSb (M = Al, In, B) for (x = 0, 0.25, 0.50, 0.75, 1) compositions has been reported using modified Becke-Johnson exchange potential (mBJ) method. In case of AlxGa1-xSb and BxGa1-xSb alloys, the bandgap values have been observed to deviate strongly from the Vegards law indicating the existence of a bowing parameter while the bandgap values of InxGa1-xSb alloys are in excellent agreement with the reported values and deviate marginally from the Vegards law. Further the optical properties, real and imaginary parts of ϵ(ω) and loss function of MxGa1-xSb (M = Al, In, B) for ternary alloys have been calculated using WC-GGA. The critical points, peaks and shoulders of imaginary part of dielectric function in these alloys have been reported. The elastic properties of these alloys, Bulk modulus (B), Shear modulus (G), Young modulus (E) and Poisson's coefficient (ν) have also been calculated using the Cubic-elastic and Tetra-elastic packages.