Electronic properties of orthorhombic BaSn₂S₅ single crystal

A theoretical investigation of the electronic structure and linear optical properties of BaSn₂S₅ compound is performed using the full-potential linearized augmented plane wave based on the local density approximation (LDA), generalized gradient approximation (GGA), Engel–Vosko GGA and the modified Becke–Johnson (mBJ) to solve the exchange correlation potential. The calculated energy gaps obtained using these approximations are 1.42, 1.59, 2.03 and 2.32 eV respectively. The mBJ shows very close agreement with the experimental energy gap (2.35 eV). The bond lengths of Ba–S and Sn–S are calculated, which are in good agreement with the experimental values. Bonds between Ba and S atoms show ionic nature, while polar covalent bonds between Sn and S atoms are obtained. The optical properties are calculated and discussed in detail. Both calculated and experimental absorption coefficients are comparable to each other in the mid-IR region. (author)