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Effect of spin contamination on the prediction of barrier heights by coupled‐cluster theory: F+H 2 →HF+H reaction
Author(s) -
Li Xiangzhu,
Paldus Josef
Publication year - 2000
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/(sici)1097-461x(2000)77:1<281::aid-qua25>3.0.co;2-d
Subject(s) - chemistry , coupled cluster , spin (aerodynamics) , hydrogen atom abstraction , atomic physics , hydrogen molecule , computational chemistry , hydrogen , molecule , thermodynamics , physics , organic chemistry
The role of spin contamination and quasidegeneracy in the energetics of a simple hydrogen abstraction reaction is studied by applying recently developed coupled‐cluster (CC) methods to an exactly solvable model for the F+H 2 →HF+H reaction [C. W. Bauschlicher and P. R. Taylor, J. Chem. Phys. 86, 858 (1987)]. To assess the role of spin contamination, the (spin)‐unrestricted Hartree–Fock (UHF) CC with singles and doubles (CCSD) barrier height is compared with that obtained with a fully spin‐adapted unitary group approach (UGA) based CCSD, while the quasidegeneracy effects are examined using the so‐called reduced multireference (RMR) CCSD method. It is shown that the effect of spin contamination on the barrier height is more significant (0.7 kcal/mol) than that of the quasidegeneracy (0.2 kcal/mol), although the latter plays a more significant role for exothermicity. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 281–290, 2000