Towards efficient orbital-dependent density functionals for weak and strong correlation

TL;DR

This paper introduces a new orbital-dependent density functional, sBGE2, that effectively handles both weak and strong electron correlation, improving accuracy across diverse chemical systems.

Contribution

It develops the sBGE2 approach and constructs the ZRPS functional, advancing the design of correlation functionals in density-functional theory.

Findings

sBGE2 accurately dissociates H2 and H2+

ZRPS outperforms other density functionals in various environments

The approach bridges weak and strong correlation regimes

Abstract

We present a new paradigm for the design of exchange-correlation functionals in density-functional theory. Electron pairs are correlated explicitly by means of the recently developed second order Bethe-Goldstone equation (BGE2) approach. Here we propose a screened BGE2 (sBGE2) variant that efficiently regulates the coupling of a given electron pair. sBGE2 correctly dissociates H$_2$ and H$_2^+$, a problem that has been regarded as a great challenge in density-functional theory for a long time. The sBGE2 functional is then taken as a building block for an orbital-dependent functional, termed ZRPS, which is a natural extension of the PBE0 hybrid functional. While worsening the good performance of sBGE2 in H$_2$ and H$_2^{+}$, ZRPS yields a remarkable and consistent improvement over other density functionals across various chemical environments from weak to strong correlation.