Towards efficient density functional theory calculations without self-interaction: The Fermi-Löwdin orbital self-interaction correction

K A Jackson,J E Peralta,R P Joshi,K P Withanage,K Sharkas,K Trepte,A I Johnson

doi:10.1088/1742-6596/1290/1/012002

Abstract

The Fermi-Löwdin orbital (FLO) approach to the Perdew-Zunger self-interaction correction (PZ-SIC) to density functional theory (DFT) is described and an improved approach to the problem of optimizing the Fermi-orbitals in order to minimize the DFT-SIC total energy is introduced. To illustrate the use of the FLO-SIC method, results are given for several applications involving problems where self-interaction errors are pronounced.

Highlights

Density functional theory (DFT) is the workhorse of computational condensed matter physics
We focus on orbital energies, which are too high in DFT calculations, making them poor approximations of electron removal energies
Fermi-Lowdin orbital (FLO)-SIC is not exact for He, but the He 1s energy level is clearly brought into much better agreement with experiment in Fermi-Lowdin orbital self-interaction correction (FLO-SIC)-LDA than in the uncorrected theory

Summary

Introduction

Density functional theory (DFT) is the workhorse of computational condensed matter physics Nowhere is this more evident than in a materials genome project where DFT calculations, typically using the Perdew-Burke-Ernzerhof (PBE) [1] generalized gradient approximation (GGA) to the exchange-correlation functional, are performed for thousands of materials to create a large database of calculated results that can be mined to discover property trends. A subtle factor in the success of this enterprise is that the calculations are done for atomic configurations at or near equilibrium In such situations PBE and similar functionals generally perform well; the reliability of these methods deteriorates when the atoms are far from equilibrium. Chemical transition states typically involve strongly stretched bonds and PBE and other functionals significantly underestimate the corresponding reaction barriers The culprit behind this breakdown is self-interaction error (SIE), which is present in all approximate semilocal density functionals due to an inexact cancellation of self-Coulomb and self-exchange-correlation energies. We conclude with a reflection on remaining challenges to implementing FLO-SIC more broadly

Theoretical background

Improving FOD optimization

Methods