Theoretical investigation of electronic and thermoelectric properties of spinel sulfides A2BS4 (A=Sc and Y; B= Cd and Zn)

Abstract

Based on first principle methods, structural, electronic and thermoelectric properties of cubic structures of spinel sulfides A2BS4 with (A = Sc and Y; B=Cd and Zn) have been investigated. We have calculated the lattice parameter a, the bulk modulus B0, its pressure derivative B’0 and the density of states (DOS) by using the full potential-linearized augmented plane wave method within the density functional theory (DFT). The computations were done by treating the exchange-correlation potential with the generalized gradient approximation (GGA) and modified Becke-Johnson potential approximation (TB-mBJ) and by using new parameters of the original TB-mBJ proposed by Koller et al. This new parameterization yields band gaps in very good agreement with experiments. The four compounds treated were found semiconductors and they have all direct bandgaps at the center of Brillouin zone (Γ). Furthermore, the thermoelectric parameters represented by the Seebeck coefficient, electrical and thermal conductivities were calculated employing the Boltzmann transport equations resolved in respect to DFT eigenvalues. Based on the obtained results, the reported parameters recommend that these spinel sulfides materials A2BS4 (A = Sc and Y; B=Cd and Zn) are suitable candidates for thermoelectric applications.