Dielectric properties of ferroelectric perovskite oxides with extended Hubbard interactions

We investigate the atomic and electronic structures of ferroelectric perovskite oxides, BaTiO₃, PbTiO₃, LiNbO₃, and BiFeO₃ using ab-initio extended Hubbard functionals (DFT+U+V), where on-site and inter-site Hubbard parameters are self-consistently determined via a pseudohybrid density functional by Agapito-Curtarolo-Buongiorno Nardelli. We compute band structures, ferroelectric distortions, polarization, Born effective charges, and switching barriers, compared with local density approximation, generalized gradient approximation (GGA), meta-GGA, and hybrid (HSE06) functionals. Results from DFT+U+V closely match experimental data, with the inter-site Hubbard terms significantly increasing band gaps, making closer alignment with GW results. The crucial role of the inter-site Coulomb interactions, restoring polar distortions suppressed by on-site U is discussed. Our approach yields accuracy comparable to HSE06 at over an order-of-magnitude lower computational cost. This combination of accuracy and efficiency makes DFT+U+V well-suited for high-throughput calculations and properties such as bulk photovoltaic effect and band alignments of ferroelectric heterostructures.