A density functional theory study of the structural, electronic, and optical properties of XGaO3 (X  =  V, Nb) perovskites for optoelectronic applications

An ab initio study using density functional theory (DFT) is carried out to explore the structural, electronic, and optical properties of vanadium gallate (VGaO3) and niobium gallate (NbGaO3). The structural properties of these compounds are determined by using the full-potential linearized augmented plane wave (FP-LAPW) technique as implemented in WIEN2k with a standard functional, i.e., the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA). In addition, the local density approximation plus Hubbard parameter (LDA + U) is employed to calculate the electronic bandgap and total and partial density of states (TDOS and PDOS), to overcome the limitation of the PBE-GGA functional in terms of underestimation of the electronic bandgap. The values computed for the indirect bandgap of VGaO3 and NbGaO3 are 0.45 and 0.51 eV, respectively, indicating that both materials are semiconductors in nature. The PDOS of the studied materials reveal that 3d-states of vanadium atoms, 4d-states of niobium atoms, and 2p-states of oxygen atoms form the valence band. Moreover, the Kramer–Kronig relations are used to compute the optical properties of the title compounds. The dielectric functions, refractive index, optical conductivity, absorption coefficient, extinction coefficient, energy loss function, and reflectivity of these materials are also computed. The results for the studied properties reveal that NbGaO3 exhibits better properties than VGaO3 for use in optoelectronic applications.