Ab initio study of the structural, electronic, phase diagram, and thermal properties of cadium beryllium selenide mixed crystals

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First-principles calculations are performed to study the structural, electronic and thermodynamic properties of technologically important Cd1−xBexSe ternary alloys using the full potential-linearized augmented plane wave method within the density functional theory. We use both PBE and Engel–Vosko generalized gradient approximations of the exchange-correlation energy that are based on the optimization of total energy and corresponding potential, respectively. The ground-state properties are determined for CdSe, BeSe and their mixed crystals at various concentrations (x=0.25, 0.5, and 0.75). Deviation of the lattice parameter from Vegard׳s law and the bulk modulus from the linear concentration dependence was observed. Using the approach of Zunger and co-workers, the microscopic origins of the band-gap bowing parameter have been explained. Through the quasi-harmonic Debye model, in which the phononic effects are considered, we have determined the thermal properties of the Cd1−xBexSe alloy such as the Debye temperature and heat capacities.