Mott gapping in 3d ABO(3) perovskites without Mott-Hubbard interelectronic repulsion energy U

Article

关键词: CHARGE DISPROPORTIONATION;    ELECTRON CORRELATIONS;    CRYSTAL-STRUCTURE;    ROOM-TEMPERATURE;    METAL-INSULATOR;    RNIO3 R;    TRANSITIONS;    EVOLUTION;    SPECTRA;    LAMNO3;   

DOI  :  10.1103/PhysRevB.100.035119

来源: SCIE

【 摘 要 】

The existence of band gaps in Mott insulators such as perovskite oxides with partially filled 3d shells has been traditionally explained in terms of strong, dynamic interelectronic repulsion codified by the on-site repulsion energy U in the Hubbard Hamiltonian. The success of the DFT-PU approach where an empirical on-site potential term U is added to the exchange- and correlation density functional theory (DFT) raised questions on whether U in DFT-PU represents interelectronic correlation in the same way as it does in the Hubbard Hamiltonian, and if empiricism in selecting U can be avoided. Here we illustrate that ab initio DFT without any U is able to predict gapping trends and structural symmetry breaking (octahedra rotations, Jahn-Teller modes, bond disproportionation) for all 3d ABO(3) perovskites from titanates to nickelates in both spin-ordered and spin-disordered paramagnetic phases. Thus, the mechanism of gap formation due to the Hubbard Hamiltonian dynamic interelectronic correlation is not a requirement in these 3d electron compounds. We describe the paramagnetic phases as a supercell where individual sites can have different local environments thereby allowing DFT to develop finite moments on different sites as long as the total cell has zero moment. We use the recently developed strongly constrained appropriately normed exchange and correlation functional (SCAN) that is sanctioned by the usual single-determinant, mean-field DFT paradigm with static correlations, but has a more precise rendering of self-interaction cancelation. Our results suggest that strong dynamic electronic correlations are not playing a universal role in gapping of 3d ABO(3) Mott insulators, and opens the way for future applications of DFT for studying a plethora of complexity effects that depend on the existence of gaps, such as doping, defects, and band alignment in ABO(3) oxides.

【 授权许可】

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