Emergence of band gaps, mass enhancement and Jahn-Teller distortions in AFM and PM 3d Oxides from polymorphous DFT*

A central feature in understanding the properties of 3d Oxides is their magnetic structure. While local moments are present both in the AFM and PM phases, the latter has traditionally been simplistically modeled as non-magnetic (NM) structure in which each atom was thought to have zero moment, (while the real condition is only that the total PM cell will have zero moment). This NM approximation underlying the N-DFT approach (N= Naive) has led to the opinion that DFT misses the Mott gap in PM insulators, effective mass enhancement effect, bond disproportionation and Jahn-Teller distortions.These discrepancies suggested in the literature invoking explicitly dynamically correlated approaches. We explored the alternative option of staying within (single determinant) DFT but getting rid of N-DFT. Instead of using a minimal unit cells, we use a supercell where the total moment is constrained to be zero but local moments and displacements that lower the total energy are allowed. This generalization creates finite band gaps in AFM and PM phases of ABO3 perovskites (except PM metals SrVO3 and CaVO3 ), disproportionation (in SmNiO3 and YNiO3), mass enhancement (in SrVO3 and doped SrTiO3) and explains the observed trends in JT distortions throughout the series.