A comprehensive DFT evaluation of catalytic and optoelectronic properties of BaTiO 3 polymorphs

BaTiO 3 exhibits promising photocatalytic characteristics and has the potential to be employed in photocatalytic water splitting and pollutant degradation. Herein, we have investigated the structural, electronic, and optical properties of BaTiO 3 in the framework of density functional theory (DFT). The obtained results are found to be consistent with theoretical results. However, using hybrid HSE06 functional, the calculated bandgap values are 3.254, 3.894, 3.694, 3.519, and 3.388 eV corresponding to cubic, rhombohedral, orthorhombic, tetragonal, and hexagonal phase of BaTiO 3 polymorphs. This is the first time a DFT calculation touched over the experimental bandgap values of BaTiO 3 polymorphs. Electronic band structure analysis revealed that all the BaTiO 3 polymorphs exhibit semiconducting character with indirect bandgap except hexagonal structure which possesses direct bandgap. The density of states (DOS), Mulliken bond analysis and charge density distribution indicates considerable hybridization between O- 2p and Ti- 3d states caused to the formation of upper valence band (VB) and lower conduction band (CB). The wide bandgap and suitable redox potential of BaTiO 3 polymorphs will be effective for water splitting as well as breakdown organic contaminants under UV–vis irradiation. The lower electron effective mass of the polymorphs indicates higher electrical conductivity. The energy dependent optical parameters show close agreement with the underlying electronic band structure. The high absorptivity, lower reflectivity and optical anisotropy (orthorhombic and tetragonal) of the polymorphs suggested that these could be a potential candidate for UV based optical device applications as well as to design wave guides, dielectric condensers and optical display devices.