Implementation of Perdew-Zunger self-interaction correction in real space using Fermi-L\"owdin orbitals

TL;DR

This paper introduces a real-space implementation of the Perdew-Zunger self-interaction correction using Fermi-L"owdin orbitals, demonstrating improved accuracy in molecular energies and reaction barriers compared to previous methods.

Contribution

The authors develop a size-extensive, real-space formulation of PZ-SIC with Fermi-L"owdin orbitals, enabling systematic convergence and large-scale parallelization.

Findings

Results closely match existing FLOSIC implementations.

Real-space results are closer to experimental data.

Scaling SIC potentials improves energy and barrier predictions.

Abstract

Most widely used density functional approximations suffer from self-interaction (SI) 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-L\"owdin 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.