Cluster expansion of the wavefunction. Symmetry-adapted-cluster expansion, its variational determination, and extension of open-shell orbital theory
The symmetry-adapted-cluster (SAC) expansion of an exact wavefunction is given. It is constructed from the generators of the symmetry-adapted excited configurations having the symmetry under consideration, and includes their higher-order effect and self-consistency effect. It is different from the conventional cluster expansions in several important points, and is suitable for applications to open-shell systems as well as closed-shell systems. The variational equation for the SAC wavefunction has a form similar to the generalized Brillouin theorem in accordance with the inclusion of the higher-order effect and the self-consistency effect. We have expressed some existing open-shell orbital theories equivalently in the conventional cluster expansion formulas, and on this basis, we have given the pseudo-orbital theory which is an extension of open-shell orbital theory in the SAC expansion formula.
- Research Organization:
- Department of Hydrocarbon Chemistry, Faculty of Engineering, Kyoto University, Kyoto, Japan and Department of Chemistry, Shiga University of Medical Science, Seta, Otsu, Japan
- OSTI ID:
- 5065657
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 68:5
- Country of Publication:
- United States
- Language:
- English
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