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Theory of biorbitals. Study of conjugated systems in their ground and excited electronic states
Author(s) -
Bessis G.,
Espagnet P.,
Bratož S.
Publication year - 1969
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.560030206
Subject(s) - excited state , conjugated system , molecule , ground state , symmetry (geometry) , charge (physics) , chemistry , matrix (chemical analysis) , physics , wave function , electronic structure , quantum mechanics , atomic physics , computational chemistry , mathematics , nuclear magnetic resonance , geometry , chromatography , polymer
The biorbital theory called also “identical geminals theory” is applied to the study of a number of conjugated molecules. All basic integrals are determined by means of the Pariser–Parr–Pople procedure. The biorbital theory reproduces about 40 per cent of the correlation energy of the ground state of the molecule; this number is raised to about 70 per cent for the lowest triplet state. The low lying excited states are well represented from the point of view of transition energy as well as from the point of view of symmetry. The occupation number matrix and the charge‐bond order matrix are defined and discussed. The overall chemical description of conjugated molecules produced by the biorbital theory is similar to that produced by other theories of electronic structure of molecules. It is concluded that the biorbital theory provides a description the quality of which is, roughly speaking, about half way between those provided by the SCF ‐ MO and complete CI theories, respectively.