Improved first-principles electronic band structure for cubic (Pm 3¯ m) and tetragonal (P4mm, P4/mmm) phases of BaTiO₃ using the Hubbard U correction

The influence of Hubbard U potential on crystal structure and electronic properties of the cubic (Pm 3¯ m) and the two tetragonal (P4mm, P4/mmm) phases of BaTiO₃ (BTO) perovskite has been investigated for the first time, using GGA-PBE approximation. Through the application of the GGA-PBE + U approximation, our results highlighted that the deviation of both lattice parameters and volume versus the experimental measurements is approximately less than 1%, and the calculated indirect band gaps of the three phases of BTO are in excellent agreement with the experimental data. The electronic investigations demonstrate that the band gap values of the three BTO polytypes, Pm 3¯ m, P4mm and P4/mmm phases, are 3.200 eV, 3.404 eV and 3.104 eV, respectively. On the other hand, the chemical bonds coupled with the DOS analysis suggest that the Ba-O and Ti-O bonds are mainly ionic and covalent, respectively. These results highlight that GGA-PBE approximation with Hubbard U correction could be an efficient method to achieve reliable band gap predictions with moderate computational cost. Hence, these findings could also be used as a theoretical reference for future research on these three phases of BTO perovskite.