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

Karol Kowalski, So Hirata, Marta Włoch, Piotr Piecuch, Theresa L. Windus

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Article number074319
JournalJournal of Chemical Physics
Issue number7
StatePublished - 2005
Externally publishedYes

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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