Koopmans' condition in self-interaction corrected density functional theory

TL;DR

This paper compares different self-interaction correction methods in density functional theory, showing that a simple average-density SIC often outperforms the more complex Perdew-Zunger SIC in calculating ionization potentials.

Contribution

It provides a comparative analysis of SIC methods, highlighting the effectiveness of the simple ADSIC over PZSIC for a wide range of molecules.

Findings

Both SIC methods improve IP calculations from HOMO levels.

ADSIC often outperforms PZSIC in accuracy.

Self-interaction correction enhances DFT ionization potential predictions.

Abstract

We investigate from a practitioner's point of view the computation of the ionization potential (IP) within density functional theory (DFT). DFT with (semi-)local energy-density functionals is plagued by a self-interaction error which hampers the computation of IP from the single-particle energy of the highest occupied molecular orbital (HOMO). The problem may be cured by a self interaction correction (SIC) for which there exist various approximate treatments. We compare the performance of the SIC proposed by Perdew and Zunger with the very simple average-density SIC (ADSIC) for a large variety of atoms and molecules up to larger systems as carbon rings and chains. Both approaches to SIC provide a large improvement to the quality of the IP if calculated from the HOMO level. The surprising result is that the simple ADSIC performs even better than the original Perdew-Zunger SIC (PZSIC) in the majority of the studied cases.