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Average virtual orbitals in configuration interaction studies with application to the low‐lying singlet states of the carbon monoxide and acetone molecules
Author(s) -
Mogensen Benny J.,
Rettrup Sten
Publication year - 1992
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.560440609
Subject(s) - atomic orbital , excited state , rydberg formula , chemistry , atomic physics , molecular orbital , singlet state , basis set , dipole , valence (chemistry) , configuration interaction , complete active space , ground state , molecule , computational chemistry , electron , density functional theory , physics , quantum mechanics , ionization , ion , organic chemistry
A method is described for obtaining a modified virtual orbital space that improves the rate of convergence in configuration interaction studies of electron correlation for both ground‐state and excited‐state properties. The validity of the method has been compared with other procedures by performing a series of test calculations of the electric dipole properties of the CO molecule in the X 1 Σ + ground state and the first excited singlet states A 1 ∏, I 1 Σ − , and D 1 Δ using different optimization schemes. The low‐lying Rydberg and valence excited states of the acetone molecule have been investigated using different N – 1‐electron potentials in the construction of virtual orbitals. The examples indicate that the presented average virtual orbitals ( AVO s) constitute a compromise set of orbitals suited for simultaneously improving the description of several electronic states. © 1992 John Wiley & Sons, Inc.