Dependence of the forbidden gap on sulfur concentration for ZnSxSe1-x solid solutions

Substitution solid solutions A(II)B(VI) demonstrate a nonlinear dependence of the forbidden gap E-g on concentration (optical deflection). The magnitude of the deflection depends on both chemical and structural factors. Atomic ordering in solution may also affect this value. Ab initio densities of states are calculated for the cubic modification of ZnSxSe1-x solid solutions (x = 0.0, 0.17, 0.33, 0.50, 0.67, 0.83, 1.0) in a virtual crystal approximation using the cluster version of the local coherent potential method in terms of full multiscattering theory. The chemical disordering effect was studied for a 50% solution with a sphalerite structure. The bond discrepancy effects were modeled for the 50% solution using ternary structures: chalcopyrite (CuFeS2 type) and ordinary tetragonal structure (CuAuI type). The calculated optical deflection parameters are in good agreement with the experimental values and with the data obtained by other authors. The calculated densities of states also agree well with the experimental X-ray and X-ray photoelectron data for the terminal compounds ZnS and ZnSe.