The effects of spurious electron self-interaction show up under various guises in density functional theory (DFT) calculations.  One important effect is that the highest occupied (HO) electron is too weakly bound in DFT, leading to a cascade of related problems: HO orbital energies are too high and therefore poor predictors of ionization energies; stable anions are unbound; molecular polarizabilities are underestimated and dipole moments are underestimated.  But it is not only HO orbital energies that are affected.   In transition metal molecules, self-interaction can alter the relative position of the 3d orbital energies, which in turn can impact the predicted oxidation state of the transition metal ion and the nature of the bonding in the molecule.  The Fermi-Löwdin orbital self-interaction correction (FLO-SIC) method was introduced to efficiently remove self-interaction errors (SIEs) from density functional theory calculations.  FLO-SIC implements the orbital-dependent Perdew-Zunger SIC energy functional in a manner that preserves unitary invariance.  Work over the past few years has shown that removing SIEs improves the DFT description of a number of properties, from HO energies, to chemical reaction barrier heights, to atomic and molecular polarizabilities.  This talk will highlight recent work on transition-metal-containing molecules, covering particular challenges presented by transition metals, algorithmic developments meant to address those challenges, and results for a number of transition metal complexes.

Correcting self-interaction errors in transition metal complexes using the Fermi-Löwdin Orbital self-interaction correction (FLO-SIC) method

ACS Spring 2022

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