Electronic and Optical Properties of γ- and -Alumina by First Principle Calculations

The electronic and optical parameters of γ-Al₂O₃ and -Al₂O₃ have been studied by using the first principle within the framework of density function theory (DFT). The computational approach is based on full-potential linearized augmented plane wave method (FP-LAPW) within the generalized gradient approximation (GGA), local density approximation (LDA), and modified Becke-Johnson potential (mBJ). The results show that these compounds have a direct gap (Γ–Γ) of about 5.375 eV and 4.716 eV for γ-Al₂O₃ and -Al₂O₃, respectively. Several optical parameters of these materials are also investigated. The values of the real part of dielectric constant are found to be 3.259 and 3.694 for γ-Al₂O₃ and -Al₂O₃, respectively, which are close to the experimental one (3.416). The refractive index is 1.806 and 1.922 for γ-Al₂O₃ and -Al₂O₃ respectively, and shows a good agreement with the experimental result which is 1.86. GGA findings are consistent with the experimental results and are better than the other approximations. There are no salient differences between GGA and LDA results. The results advocate using this material as a transparent conducting layer in solar cell structure, which can be operated in a wide energy range.