Universität zu Köln

Herrmann, Nils ORCID: 0000-0002-6468-9180 and Hanrath, Michael . Analysis of different sets of spin-adapted substitution operators in open-shell coupled cluster theory. Mol. Phys.. ABINGDON: TAYLOR & FRANCIS LTD. ISSN 1362-3028

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Abstract

In spin-adapted open-shell coupled cluster (CC) theory, the choice of spin-free spatial substitution operators is generally not unique. Due to an increasing linear dependence of the cluster operator (with increasing substitution level), the options to span identical linear spaces increase rapidly. In this work, several sets of non-orthogonal as well as orthogonal spin-adapted substitution operators are generated and used in consecutive configuration interaction (CI) and CC calculations. All (full) operator sets were generated to span the same linear space. The results are analysed in terms of the produced wave function quality and the amount of recovered correlation energy w.r.t. full CI (FCI). In particular, the influence of different amounts of spectators, orthogonality as well as spin incompleteness was investigated. It was found that CC calculations involving fewer spectators lead to more accurate results in general. Here, correlation energy differences of up to 0.32% for minimal to maximal spectating sets were obtained. As expected, all conducted calculations led to identical results for non-orthogonal and orthogonal operator sets. Spin completeness was found to be of great importance. Spin-incomplete cluster operators led to significant errors in both the correlation energies and the FCI overlap.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Herrmann, Nils UNSPECIFIED orcid.org/0000-0002-6468-9180 UNSPECIFIED Hanrath, Michael UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-566843
DOI:	10.1080/00268976.2021.2005836
Journal or Publication Title:	Mol. Phys.
Publisher:	TAYLOR & FRANCIS LTD
Place of Publication:	ABINGDON
ISSN:	1362-3028
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language LINEAR-RESPONSE CALCULATION; AUTOMATED IMPLEMENTATION; APPROXIMATE ACCOUNT; EXCITED CLUSTERS; STATE-UNIVERSAL; SINGLE; SYSTEMS; CONTAMINATION; FORMALISM; ADAPTATION Multiple languages Chemistry, Physical; Physics, Atomic, Molecular & Chemical Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/56684