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A study of 1A1-3B1 separation in CH2 using orthogonally spin-adapted state-universal and state-specific coupled-cluster methods

✍ Scribed by Xiangzhu Li; Piotr Piecuch; Josef Paldus

Publisher: Elsevier Science
Year: 1994
Tongue: English
Weight: 753 KB
Volume: 224
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(94)00563-x

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✦ Synopsis

The orthogonally spin-adapted (OSA) state-universal coupled-cluster method involving singly and doubly excited clusters (CCSD) and the recently proposed OSA open-shell state-specific CCSD method are applied to the problem of singlet-triplet separation in methylene. Both double zeta (DZ) and DZ plus polarization bases are utilized. Comparison with other correlation treatments, including limited and full confiiuration interaction and various many-body approaches based on multi-configurational self-consistent-field reference, indicates that our method represents a highly efficient theoretical tool that can lead to reliable predictions of the 'A1-3B, splitting in CHz when larger bases are employed.

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An ab initio determination of 1A1-3B1 energy gap in CH2 using orthogonally spin-adapted state-universal and state-specific coupled-cluster methods

✍ Piotr Piecuch; Xiangzhu Li; Josef Paldus 📂 Article 📅 1994 🏛 Elsevier Science 🌐 English ⚖ 967 KB

The orthogonally spin-adapted open-shell state-universal (SU) and state-specific (SS) single and double coupled-cluster methods (CCSD) are applied to the singlet-triplet separation in methylene. Calculations have been performed using atomic-naturalorbital basis [ 5s4p3d2flg/3s2pid] and a few smaller