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Partially linearized external models to active‐space coupled‐cluster through connected hextuple excitations
Author(s) -
Xu Enhua,
Tenno Seiichiro L.
Publication year - 2018
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.25163
Subject(s) - coupled cluster , diatomic molecule , dissociation (chemistry) , bond dissociation energy , physics , cluster (spacecraft) , scaling , space (punctuation) , chemistry , potential energy , bond length , atomic physics , molecule , quantum mechanics , mathematics , computer science , geometry , programming language , operating system
Partially linearized external models to active‐space coupled‐cluster through hextuple excitations, for example, CC{SDtqph} L , CCSD{tqph} L , and CCSD{tqph} hyb, are implemented and compared with the full active‐space CCSDtqph. The computational scaling of CCSDtqph coincides with that for the standard coupled‐cluster singles and doubles (CCSD), yet with a much large prefactor. The approximate schemes to linearize the external excitations higher than doubles are significantly cheaper than the full CCSDtqph model. These models are applied to investigate the bond dissociation energies of diatomic molecules (HF, F 2 , CuH, and CuF), and the potential energy surfaces of the bond dissociation processes of HF, CuH, H 2 O, and C 2 H 4 . Among the approximate models, CCSD{tqph} hyb provides very accurate descriptions compared with CCSDtqph for all of the tested systems. © 2018 Wiley Periodicals, Inc.