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Orbital correlation diagrams based on multiconfigurational variation of moments I. Theory
Author(s) -
MüllerRemmers Peter L.,
Jug Karl
Publication year - 1985
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.560280604
Subject(s) - open shell , formalism (music) , configuration interaction , complete active space , chemistry , operator (biology) , quantum mechanics , slater determinant , physics , molecular orbital , atomic physics , computational chemistry , atomic orbital , molecule , visual arts , gene , electron , art , musical , biochemistry , repressor , transcription factor
A multiconfigurational variation of moments ( MCM ) is presented to determine correlated orbital energies. Appropriate multiconfigurational one‐particle operators are introduced starting for closed‐shell systems from the restricted Hartree–Fock ( RHF ) scheme and for open‐shell system from the unrestricted Hartree–Fock ( UHF ) scheme. The advantage of these operators is the linear form of the correlation energy in the configuration interaction ( CI ) coefficients. They obey HF analogous pseudoeigenvalue equations and are therefore a generalization of the HF operator. In principle, the scheme can be extended to a multiconfiguration self‐consistent field ( MCSCF ) procedure for moments. In contrast to the SCF formalism they allow an orbital description of degeneracy and quasidegeneracy of the highest occupied ( HOMO ) and lowest unoccupied ( LUMO ) molecular orbital. With these operators, funnels of thermally forbidden Woodward–Hoffman reactions, as well as dissociations, can be described in a physically meaningful fashion by orbitalcorrelation diagrams.