Improved pseudopotential transferability for magnetic and electronic properties of binary manganese oxides from DFT + U + J calculations

We employ the fully anisotropic $\mathrm{DFT}+U+J$ approach with the PBEsol functional to investigate ground-state magnetic and electronic properties of bulk binary manganese oxides: MnO, ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}, \ensuremath{\alpha}\ensuremath{-}{\mathrm{Mn}}_{2}{\mathrm{O}}_{3}$, and $\ensuremath{\beta}\ensuremath{-}{\mathrm{MnO}}_{2}$, in order of increasing Mn valence. The computed crystal structures, noncollinear magnetic ground states, and corresponding electronic structures are in good agreement with the experimental data and hybrid functional calculations available in the literature. We take into account the nonlinear core-valence interaction in our Mn pseudopotential designed by ourselves, as it has been proven to be important for transition-metal systems. Although the Hubbard $U$ term is capable by itself of opening a band gap, the explicitly defined exchange parameter $J$ plays an important role in improving the detailed electronic and noncollinear magnetic structure profiles. Appropriate band gaps are obtained with $U$ values smaller than those used in previously reported calculations. Our results suggest that pseudopotential design together with $\mathrm{DFT}+U+J$ enables the acquisition of accurate properties of complex magnetic systems using a nonhybrid density functional.