Cluster expansion of the wavefunction. Symmetry-adapted-cluster expansion, its variational determination, and extension of open-shell orbital theory
- 1 March 1978
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 68 (5), 2053-2065
- https://doi.org/10.1063/1.436028
Abstract
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.Keywords
This publication has 47 references indexed in Scilit:
- An equations of motion approach for open shell systemsThe Journal of Chemical Physics, 1975
- What is the best expression of the second-order sum-over-state perturbation energy based on the Hartree-Fock wavefunction?The Journal of Chemical Physics, 1974
- General SCF operator satisfying correct variational conditionThe Journal of Chemical Physics, 1973
- Theory of Atomic Structure Including Electron Correlation. I. Three Kinds of Correlation in Ground and Excited ConfigurationsPhysical Review B, 1969
- Improved Quantum Theory of Many-Electron Systems. III. The GF MethodThe Journal of Chemical Physics, 1968
- Variational approach to the many-body problemNuclear Physics, 1965
- Cluster expansion of operator averages for systems of many particlesNuclear Physics, 1963
- Vibrational states of nuclei in the random phase approximationNuclear Physics, 1961
- Stability conditions and nuclear rotations in the Hartree-Fock theoryNuclear Physics, 1960
- Bound states of a many-particle systemNuclear Physics, 1958