Modeling The Structural And Electronic Properties Of Tetragonal BaTiO3: A Comparative Study Using Density Functional And Many-Body Approaches

Abstract

The accurate description of the structural and electronic properties of tetragonal BaTiO3 remains a challenge for density functional theory (DFT) due to self-interaction errors, particularly in the partially filled Ti(3d) orbitals. In this work, we systematically investigate the performance of sev eral first-principles approaches, including Perdew–Burke–Ernzerhof revised for solids (PBEsol), PBEsol+U, PBEsol+U+V, HSE06, and G0W0+Bethe–Salpeter equation (BSE), for modeling the structural and electronic properties of this prototypical ferroelectric oxide. The on-site Hubbard U(Ti(3d)) and intersite V (Ti(3d)–O(2p)) parameters are computed self-consistently using dens ity functional perturbation theory. We show that PBEsol+U incorrectly stabilizes the cubic phase by suppressing Ti–O hybridization, whereas the inclusion of the intersite V term restores the tet ragonal structure, yielding accurate lattice parameters and atomic displacements. Among the methods considered, PBEsol+U+V provides the best agreement with experimental structural data. All approaches predict an indirect band gap, with PBEsol significantly underestimating its value. Hybrid HSE06 and G0W0+BSE calculations yield substantially improved band gaps, with G0W0+BSE predicting 3.30 eV, in close agreement with experiment. While PBEsol+U+V improves the electronic structure relative to semilocal DFT, it remains less accurate than hybrid and many-body approaches. These results clarify the role of intersite interactions in stabilizing the ferroelectric phase of BaTiO3 and highlight the strengths and limitations of commonly used electronic-structure methods for modeling complex oxides.