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Symmetry breaking and electron correlation in O 2 − , O 2 , and O 2 + : A comparison of coupled cluster and quadratic configuration interaction approaches
Author(s) -
Chandrasekher Charu A.,
Griffith K. S.,
Gellene Gregory I.
Publication year - 1996
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(1996)58:1<29::aid-qua4>3.0.co;2-#
Subject(s) - configuration interaction , cluster (spacecraft) , physics , electronic correlation , atomic physics , symmetry breaking , symmetry (geometry) , electron , coupled cluster , full configuration interaction , chemistry , excited state , nuclear physics , quantum mechanics , molecule , mathematics , geometry , computer science , programming language
Potential energy curves are calculated for O 2 − , O 2 , and O 2 + at the CCSD, QCISD, CCSD(T), and QCISD(T) levels of theory using aug‐cc‐pVDZ and aug‐cc‐pVTZ basis sets with electron correlation built onto inversion symmetry constrained and relaxed UHF wave functions. The spectroscopic constant r e , w e , w e , x e , D j , and α e , are determined from the potential curves using standard second‐order perturbation theory expressions and are compared with experimental values to assess the relative accuracy of the theoretical approaches. Comparison of corresponding symmetry‐constrained and symmetry‐relaxed calculations indicates that the CCSD method is generally superior to CCSD(T), QCISD, and QCISD(T) in recovering from a symmetry‐broken reference function. © 1996 John Wiley & Sons, Inc.