Active-space coupled-cluster study of electronic states of Be 3

The active-space coupled-cluster (CC) and equation-of-motion (EOM) CC methods with all single and double excitations with triple excitations defined via active orbitals (CCSDt, EOMCCSDt), as implemented with TENSOR CONTRACTION ENGINE , are applied to the challenging Be 3 system, which is characteriz...

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Bibliographic Details
Published in:The Journal of chemical physics 2005-08, Vol.123 (7), p.074319-074319-6
Main Authors: Kowalski, Karol, Hirata, So, Włoch, Marta, Piecuch, Piotr, Windus, Theresa L.
Format: Article
Language:English
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Summary:The active-space coupled-cluster (CC) and equation-of-motion (EOM) CC methods with all single and double excitations with triple excitations defined via active orbitals (CCSDt, EOMCCSDt), as implemented with TENSOR CONTRACTION ENGINE , are applied to the challenging Be 3 system, which is characterized by a large number of low-lying excited states dominated by two-electron transitions and significant high-order correlation effects in the ground electronic state. It is demonstrated that the CCSDt and EOMCCSDt methods provide an excellent description of complicated electronic quasidegeneracies present in the Be 3 cluster. Different strategies for defining triple excitations within the CCSDt∕EOMCCSDt approach are discussed.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.2001656