We used an ab initio full potential-linearized augmented plane wave technique within the density functional theory to study the structural and optoelectronic properties of Ag ₂HgSnS ₄ in a wurtzite-stannite phase. The exchange correlation effects are included through the generalized gradient approximation and modified Becke-Johnson exchange potential. Various physical quantities, such as lattice parameter, bulk modulus, band structure and density of states, are given. Also, we have presented the results of the effective mass for the electrons in the CB and the holes in the BV. We show that the modified Becke-Johnson exchange potential can predict the energy band gap in better agreement with the experiment. In addition the dielectric function and energy-loss function are presented for the energy range of 0-26 eV. The electronic and optical properties indicate that this compound can be successfully used in optoelectronic devices

The electronic and optical properties of M ₂S (M = Li, Na, K and Rb) compounds in the cubic antifluorite structure have been calculated, using a full relativistic version of the full-potential augmented plane-wave plus local orbitals method based on density functional theory, within both the local density approximation (LDA) and the generalized gradient approximation (GGA). Moreover, the Engel–Vosko GGA formalism (EV-GGA) is applied so as to optimize the corresponding potential for band structure calculations. The calculated equilibrium lattices and bulk moduli are in good agreement with the available data. Band structure, density of states, electron charge density and pressure coefficients of energy gaps are given. Results obtained for band structure using EV-GGA are larger than those with LDA and GGA. It is found that the spin–orbit coupling lifts the triple degeneracy at the Γ point and the double degeneracy at the X point. The analysis of the electron charge density...

The full potential–linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) was applied to study the structural, electronic and thermodynamic properties of MgS _x Se _{1− x}, MgS _x Te _{1− x} and MgSe _x Te _{1− x} ternary alloys. The calculated lattice parameters at different compositions of MgS _x Se _{1− x} and MgSe _x Te _{1− x} alloys were found to vary almost linearly, while a significant deviation of the lattice parameter from Vegard's law for MgS _x Te _{1− x} alloy was observed. This is mainly due to the large mismatch of the lattice parameters of the binary compounds MgS and MgTe. A large deviation of the bulk modulus from linear concentration dependence (LCD) was observed for all three alloys. The calculated optical bowing was found to be mainly caused by the structura...