Active-Space Coupled-Cluster Study of Electronic States of Be₃

Journal Article · Mon Aug 15 00:00:00 EDT 2005 · Journal of Chemical Physics, 123(074319 (6 pages)

DOI:https://doi.org/10.1063/1.2001656· OSTI ID:859426

Kowalski, Karol; Hirata, So; Wloch, M W; Piecuch, Piotr; Windus, Theresa L

An automated implementation of the active-space coupled-cluster (CC) and equation-of-motion (EOM) CC methods with all singles and doubles, and triples defined via active orbitals (CCSDt, EOMCCSDt) employing Tensor Contraction Engine (TCE), is reported. The TCE-generated CCSDt/ codes are parallel and applicable to closed-and open-shell references. The effectiveness of the new code in describing electronic quasi-degeneracies is illustrated by the CCSDt / EOMCCSDt) calculations for the challenging Be₃system, 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. Different strategies for defining triple excitation s within the CCSDt / EOMCCSDt) approach are discussed.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 859426
• Report Number(s): PNNL-SA-45585; 3565; KP1301030
• Journal Information: Journal of Chemical Physics, 123(074319 (6 pages), Journal Name: Journal of Chemical Physics, 123(074319 (6 pages)
• Country of Publication: United States
• Language: English

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