Department of Chemistry, Faculty of Science, Osaka University, Osaka 560, Japan.
Instability in chemical bonds. II. Theoretical studies of exchange-coupled open-shell systems
Article first published online: 19 OCT 2004
Copyright © 1993 John Wiley & Sons, Inc.
International Journal of Quantum Chemistry
Supplement: Proceedings of the International Syposium on Atomic, Molecular, and Condensed Matter Theory and Computational Methods
Volume 48, Issue Supplement 27, pages 501–515, 13/20 March 1993
How to Cite
Yamaguchi, K., Okumura, M., Takada, K. and Yamanaka, S. (1993), Instability in chemical bonds. II. Theoretical studies of exchange-coupled open-shell systems. Int. J. Quantum Chem., 48: 501–515. doi: 10.1002/qua.560480848
- Issue published online: 19 OCT 2004
- Article first published online: 19 OCT 2004
- Manuscript Received: 8 JUL 1993
The electronic and geometrical structures of exchange-coupled open-shell systems such as bis(methylene) methane and the chromium–methylene cation were investigated by the molecular orbital and its extended methods: RHF, UHF, UNO-CAS, RMP, UMP, PUMP, APUMP, UCCSD(T), UNO-CI and QCISD(T). The fully optimized geometries of these species by the energy gradients of UMPn solutions are consistent with the experimental values. The total energies of the lowest and highest spin states were calculated in order to elucidate the effective exchange integrals in the Heisenberg model for methylene and bis(methylene) methane. The spin projection is necessary for the UHF-based wavefunctions in the lowest spin state of the species. The binding energies for the chromium cation–methylene double bond were calculated by both spin-unprojected and -projected methods. It was found that the binding energy between Cr+ and 3CH2 by APUHFQCISD(T) is in accord with the experimental value. © 1993 John Wiley & Sons, Inc.