Reducing charge delocalization error of density functional theory

TL;DR

This paper introduces a modified density functional that effectively reduces charge delocalization errors, improves dissociation predictions, and outperforms existing functionals in various tests, enhancing the accuracy of density functional theory.

Contribution

The authors develop a new functional that simultaneously addresses charge delocalization error and nondynamic correlation, improving upon previous functionals in accuracy and reliability.

Findings

Eliminates spurious barriers in symmetric charged dimer dissociation.

Accurately localizes positive charge in molecular clusters.

Outperforms existing functionals on the SIE4x4 set.

Abstract

The charge delocalization error, besides nondynamic correlation, has been a major challenge to density functional theory. Contemporary functionals undershoot the dissociation of symmetric charged dimers A2+, a simple but stringent test, predict a spurious barrier and improperly delocalize charges for charged molecular clusters. We extend a functional designed for nondynamic correlation to treat the charge delocalization error by modifying the nondynamic correlation for parallel spins. The modified functional eliminates those problems and reduces the multielectron self-interaction error. Furthermore, its results are the closest to those of CCSD(T) in the whole range of the dissociation compared with contemporary functionals. It correctly localizes the net positive charge in (CH4)n+ clusters and predicts a nearly constant ionization potential as a result. Testing of the SIE4x4 set shows that the new functional outperforms a wide variety of functionals assessed for this set in the literature. Overall, we show the feasibility of treating charge delocalization together with nondynamic correlation.