Implementation of Perdew-Zunger self-interaction correction in real space using Fermi-Lowdin orbitals

Most widely used density functional approximations suffer from self-interaction error, which can be corrected using the Perdew-Zunger (PZ) self-interaction correction (SIC). We implement the recently proposed size-extensive formulation of PZ-SIC using Fermi-Lowdin Orbitals (FLOs) in real space, which is amenable to systematic convergence and large-scale parallelization. We verify the new formulation within the generalized Slater scheme by computing atomization energies and ionization potentials of selected molecules and comparing to those obtained by existing FLOSIC implementations in Gaussian based codes. The results show good agreement between the two formulations, with new real-space results somewhat closer to experiment on average for the systems considered. We also obtain the ionization potentials and atomization energies by scaling down the Slater statistical average of SIC potentials. The results show that scaling down the average SIC potential improves both atomization energies and ionization potentials, bringing them closer to experiment. Finally, we verify the present formulation by calculating the barrier heights of chemical reactions in the BH6 dataset, where significant improvements are obtained relative to Gaussian based FLOSIC results.

Automated summary

The study addresses the self-interaction error in widely used density functional approximations, proposing a new real-space size-extensive formulation of PZ-SIC. The results show improved accuracy in calculating atomization energies and ionization potentials, with scaling down the average SIC potential bringing the results closer to experimental values. Additionally, significant improvements are observed in calculating barrier heights of chemical reactions compared to Gaussian based FLOSIC results.