Structural, electronic and thermodynamic properties of magnesium chalcogenide ternary alloys

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 MgSxSe1-x, MgSx Te1-x and MgSex Te1-x ternary alloys. The calculated lattice parameters at different compositions of MgSxSe1-x and MgSex Te1-x alloys were found to vary almost linearly, while a significant deviation of the lattice parameter from Vegard's law for MgSx Te1-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 structural relaxation. Moreover, a significant charge exchange contribution was observed in the case of MgSx Te1-x alloy. The calculated phase diagram shows a broad miscibility gap for these alloys with a high critical temperature.