Assessing combinations of singlet-paired coupled cluster and density functional theory for treating electron correlation in closed and open shells

Abstract

Singlet-paired coupled cluster doubles (CCD0) is a modification of symmetry-adapted coupled cluster doubles (CCD) that simplifies the doubles excitation operator in order to better describe static correlation, but at the cost of missing a fraction of the dynamical correlation. Methods to recover the correlation missed by CCD0 using density functional theory (DFT) have been developed for closed-shell systems and have been found to accurately describe a number of ground-state properties of singlet molecules. In this work, we extend these CCD0+DFT models for use in open-shell systems and benchmark the new methods on a number of chemical quantities, the accurate description of which requires a balanced treatment of electron correlation in both closed and open shells.

GRAPHICAL ABSTRACT

KEYWORDS:

• Electron correlation
• coupled-cluster theory
• singlet-triplet splittings
• barrier heights
• density functional theory

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

John A. Gomez http://orcid.org/0000-0001-6623-3702

Additional information

Funding

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry Program under Award Number DE-FG02-04ER15523 G.E.S. is a Welch Foundation Chair (C-0036). J.A.G. acknowledges the support of the National Science Foundation Graduate Research Fellowship Program (DGE-1450681) and the Lodieska Stockbridge Vaughn Fellowship.