First principles study of 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.