Correction to constrained coupled cluster doubles models based on the second coupled cluster central moment

David W Small; Martin Head-Gordon

doi:10.1063/1.2752812

Correction to constrained coupled cluster doubles models based on the second coupled cluster central moment

J Chem Phys. 2007 Aug 14;127(6):064102. doi: 10.1063/1.2752812.

Authors

David W Small¹, Martin Head-Gordon

Affiliation

¹ Department of Chemistry, University of California, Berkeley, California 94720, USA.

PMID: 17705583
DOI: 10.1063/1.2752812

Abstract

We develop a correction for the coupled cluster version of the perfect pairing (PP) model. The correction is based on finding modified values of the PP amplitudes such that the second coupled cluster central moment defined in the space of all valence single and double substitutions vanishes and, subject to this constraint, minimizing the deviation between the modified and unmodified PP amplitudes with respect to a chosen metric. We discuss how this correction can be generalized to other constrained doubles models, such as local correlation and active-space models. While the correction is not strictly size consistent and retains some of the deficiencies of the PP model, numerical results indicate that much of the missing active-space coupled cluster singles and doubles correlation energy is recovered.