First-principles studies of electronic, optical, and mechanical properties of γ-Bi₂Sn₂O₇

The detailed theoretical studies of electronic, optical, and mechanical properties of γ-Bi₂Sn₂O₇ are carried out by using first-principle density functional theory calculations. Our calculated results indicate that γ-Bi₂Sn₂O₇ is the p-type semiconductor with an indirect band gap of about 2.72 eV. The flat electronic bands close to the valence band maximum are mainly composed of Bi-6s and O-2p states and play a key role in determining the electrical properties of γ-Bi₂Sn₂O₇. The calculated complex dielectric function and macroscopic optical constants including refractive index, extinction coefficient, absorption coefficients, reflectivity, and electron energy-loss function show that γ-Bi₂Sn₂O₇ is an excellent light absorbing material. The analysis on mechanical properties shows that γ-Bi₂Sn₂O₇ is mechanically stable and highly isotropic.