Fundamental properties of scandium chalcogenides and their alloys: DFT study

The full-potential linearized-augmented plane wave calculations based on density functional theory are performed to study the structural, electronic, optical and thermodynamic properties of scandium chalcogenides Sc X ( X = S, Se, Te) and their ternary alloys at equilibrium as well as under pressure. The revised Perdew–Burke–Ernzerhof generalized gradient approximation (GGA) is used to calculate the structural properties. The electronic and optical properties are calculated employing the GGA and the modified Becke–Johnson (mBJ) approaches. Moreover, the calculated lattice parameters agree well with the experiment results. The structure NaCl-type (B1) of the scandium chalcogenides undergoes under pressure a structural phase transition to CsCl-type (B2) and ZnS-type (B3). The binary and ternary alloys indicate a metallic behavior using GGA and mBJ scheme. The interband contribution to the optical properties is investigated by calculating the dielectric parameters ε 1 ( ω ), ε 2 ( ω ) and the index of refraction n ( ω ). A quasi-harmonic Debye model is applied to calculate the thermal properties.