Mitigating Self-Interaction Error in Transition-Metal Oxides with Novel r²SCANY@r²SCANX Methods

A recent meta-generalized gradient approximation, the restored-regularized strongly constrained and appropriately normed (r²SCAN) XC functional, fulfils 17 exact constraints of the XC energy and improves accuracy for molecules and materials. However, r²SCAN still struggles with open d and f transition-metal compounds’ properties such as band gaps, magnetic moments, and oxidation energies. Its inaccuracies mainly stem from functional- and density-driven errors due to DFT self-interaction error. Here, we propose a novel method, r²SCANY@r²SCANX, to mitigate the pernicious self-interaction error of XC functionals for accurate simulations of electronic, magnetic, and thermochemical properties of transition-metal oxides. r²SCANY@r²SCANX uses different fractions of exact Hartree–Fock exchange: X to define the electronic density, and Y to set the density functional approximation for the energy. We show that r²SCANY@r²SCANX simultaneously addresses functional- and density-driven inaccuracies, mitigating self-interaction error in DFT. With only 1 (or at most 2) universal parameters, r²SCANY@r²SCANX improves upon r²SCAN predictions for 18 correlated oxides and even outperforms the highly parameterized DFT(r²SCAN)+U method—the state-of-the-art approach to strongly correlated materials.