Electronic, dielectric and optical properties of orthorhombic lanthanum gallate perovskite

The electronic structure, dielectric and optical properties of orthorhombic LaGaO3 perovskite were investigated using first-principles calculations based on the density functional theory. Various density functional approximations were adopted, including GGA-PBEsol functional, meta-GGA-MBJ functional, HSE06 functional, and HSE (15%) functional (containing 15% screened Hartree-Fock exchange functional). After the full relaxation of LaGaO3, the calculated lattice parameters were in great agreement with other experimental and theoretical results. The dielectric function, absorption coefficient, reflectivity, conductivity, refractive index, and electron energy-loss spectrum were calculated and discussed in detail. Results of band structure exhibited the indirect band gap of LaGaO3 with the value of 4.48 eV derived from HSE (15%) functional, which is in good agreement with the experimental value of 4.4eV. Strong hybridization between Ga atom and O atom, as well as the hybridization between La atom and O atom was observed from the density of states and electron charge density, revealing mixed bonding characteristic which is the essential for the ferroelectricity of orthorhombic LaGaO3. (C) 2017 Elsevier B. V. All rights reserved.