The ground state total energy in density functional theory (DFT) is subject to the stringent flat-plane condition by Mori-Sanchez, Cohen, and Yang: piecewise-linear in fractional charge and constant in fractional spin. This condition is violated in approximate exchange-correlation functionals, leading to severe delocalization errors and static correlation errors in DFT calculations. We propose an approach that naturally satisfies the flat-plane condition for the correlated sub-space of electrons, corrects both types of errors, and incorporates explicit derivative discontinuity. Our density matrix minimization (DMM) method, based on a variational minimization of the electronic interactions with respect to the Fock space many-body density matrix, can be solved uniquely and efficiently. We present a few case studies including normal metals, magnetic metals and Mott insulators.

Unified treatment of derivative discontinuity, delocalization, and static correlation effects in DFT: The LDA plus Density Matrix Minimization (LDA+DMM) method

2019 Spring National Meeting

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