Self-interaction effects in molecular dissociation curves*

The Fermi-Löwdin Orbital Self Interaction Correction (FLO-SIC) removes unphysical electron self-interaction from Density Functional Theory (DFT), the most widely used first-principles method in condensed matter and chemical physics. Self-interaction errors can be particularly pronounced in situations where bonds are stretched, such as when an atom is dissociated from a molecule. To study the effectiveness of FLO-SIC in this context, we calculated dissociation curves corresponding to removing one H atom from each of the molecules LiH, BeH₂, BH₃, …, HF, and one F atom from each of LiF, F_2,and FCl. To get a statistical measure of performance, we compare FLO-SIC-DFT and DFT dissociation energies to accurate reference energies at four points along each curve. We find that FLO-SIC improves the performance of the local density approximation (LDA) at all separations, while for the generalized gradient approximation in the Perdew-Burke-Ernzerhof (PBE) form the performance is improved only for large separations. FLO-SIC corrects the tendency of both LDA and PBE to predict charged fragments in the large separation limit.