Connected quadruple excitations in the coupled-cluster theory

The role of the connected quadruple excitations in the coupled-cluster (CC) theory is discussed. The full inclusion of the T 4 (Q) operator in addition to singles (S), doubles (D) and triples (T) defines the CCSDTQ method which offers a very accurate computational tool applicable to small molecular...

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Bibliographic Details
Published inMolecular physics Vol. 108; no. 21-23; pp. 2975 - 2985
Main Authors Kucharski, Stanisław A., Musiał, Monika
Format Journal Article
LanguageEnglish
Published Abingdon Taylor & Francis Group 10.11.2010
Taylor & Francis Ltd
Taylor & Francis
Subjects
Approximation
Configuration interaction
coupled-cluster method
Coupling (molecular)
Excitation
Factorization
Mathematical analysis
Molecular physics
quadruple excitations
quasilinear form of equations
Physical Sciences
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Summary:The role of the connected quadruple excitations in the coupled-cluster (CC) theory is discussed. The full inclusion of the T 4 (Q) operator in addition to singles (S), doubles (D) and triples (T) defines the CCSDTQ method which offers a very accurate computational tool applicable to small molecular systems. The efficient organization of the CC equations results in the quasilinear formulation of the CCSDTQ scheme. A wider range of applications can be ensured with the approximate variants of the CCSDTQ approach. Due to possible factorization of the lowest order quadruple contribution to the energy, a noniterative scheme has been formulated which requires n 7 scaling. Performance of the CCSDTQ method has been discussed on the basis of the results obtained for several small molecules in confrontation with the reference full configuration interaction data.
Bibliography:ObjectType-Article-2
SourceType-Scholarly Journals-1
ObjectType-Feature-1
content type line 23
ISSN:0026-8976
1362-3028
DOI:10.1080/00268976.2010.523523