Prediction of Mott insulation and atomic displacements in 3d ABO₃ oxide perovskites without Hubbard U

The existence of insulating band gaps in both spin-ordered and disordered phases of 3d ABO₃ perovskite oxides has been traditionally ascribed within the Mott picture to the formation of a two-electron state on a 3d site and an empty 3d site; the separation between these upper-Hubbard and lower-Hubbard states is the interelectronic repulsion U. The observed structural distortions such as bond disproportionation or Jahn-Teller motions appear as secondary effects. The non-spin polarized DFT approach gives zero gap, a result that was used in the literature as a basis to argue that DFT fails. We apply to all ABO₃ 3d perovskites DFT with (i) fully relaxed large supercells (ii) using XC functionals that have small delocalization errors (DFT+U and SCAN without U) and (iii) occupying single partners in degenerate levels. We find DFT even without U capture gapping trends and structural distortions in ABO₃ materials ranging from titanates to nickelates in both AFM and PM phases. Our results thus suggest that dynamical correlations are not playing a universal role in gapping of 3d ABO₃ insulators, and demonstrate that DFT is a viable platform fully able to model their ground states.