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C 2 V Insertion pathway for BeH 2 : A test problem for the coupled‐cluster single and double excitation model
Author(s) -
Purvis George D.,
Shepard Ron,
Brown Franklin B.,
Bartlett Rodney J.
Publication year - 1983
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560230307
Subject(s) - coupled cluster , excitation , configuration interaction , full configuration interaction , atomic physics , valence (chemistry) , chemistry , cluster (spacecraft) , field (mathematics) , physics , quantum mechanics , molecule , mathematics , excited state , computer science , pure mathematics , programming language , organic chemistry
The coupled‐cluster single and double excitation model ( CCSD ) is applied to an energy path for the insertion of Be into H 2 and compared to the full configuration interaction ( FCI ) and full valence–multiconfiguration self‐consistent field ( FV – MCSCF ) results. This model problem is a severe test of a single‐reference‐function correlated method since two configurations are heavily weighted in the FCI description. CCSD is demonstrated to describe the FCI results using a single reference function which, however, changes orbital characteristics along the sampling path. In this case CCSD gives excellent agreement with the FCI results.