Longuet-Higgins model

Pople-Longuet-Higgins model, Renner-Teller effect ... 

Zahradnik and Koutecky made a series of molecular orbital calculations by the HMO method, using the Longuet-Higgins model for the sulfur atom, on thiazole and the isomeric thiadiazoles. They found the largest 7r-electron stabilization for the 1,2,4 isomer, but very little dilFerence between the 1,2,5 and 1,3,4 isomers. The calculated bond orders, however, show a larger 7r-electron delocalization in the 1,2,5 than in the 1,3,4 isomer, in agreement with the results of Bak et The formal double bonds have a lower bond order in the 1,2,5 than in the 1,3,4 isomer, whereas the reverse is true for the formal single bonds. These relations hold for three different sets of parameters for the carbon-sulfur bond. 

As mentioned earlier, it is possible to calculate the interference signal directly from (3.5) without resorting to adiabatic or locally quadratic approximations, by diagonalizing the Longuet-Higgins model Hamiltonian with the standard procedure [10]. Figure 1 shows the exact interfer-... 

For polyacetylene, many authors apply the so-called SSH Hamiltonian introduced by Su, Schrieffer, and Heeger (1980), which is an alternative to the Longuet-Higgins model. The difference is only in the handling of the a core potential function f and in the parametrization of the model. 

Stillinger F 1973 Structure in aqueous solutions from the standpoint of scaled particle theory J. Solution Chem. 2 141 Widom B 1967 Intermolecular forces and the nature of the liquid state Sc/e/ ce 375 157 Longuet-Higgins H C and Widom B 1964 A rigid sphere model for the melting of argon Mol. Phys. 8 549... 

Appendix A The Jahn-Teller Model and the Herzberg-Longuet-Higgins Phase Appendix B The Bom-Oppenheimer Treatment Appendix C Formulation of the Vector Potential References... 

APPENDIX A THE JAHN-TELLER MODEL AND THE HERZBERG-LONGUET-HIGGINS PHASE... 

In the approach of Dewar and co-workers (34), termed the half-electron method , a physical model is considered in which an unpaired electron is replaced by two hypothetical half-electrons of opposite spin. For radicals containing one unpaired electron, the eigenvalue problem of this method is, in our opinion, identical with the method of Longuet-Higgins and Pople (27) ... 

Herzberg-Longuet-Higgins phase-based treatment, Jahn-Teller model, 185-186 Jahn-Teller systems, Longuet-Higgins phase, 119-122... 

Longuet-Higgins phase-based treatment, three-particle reactive system, 157-168 theoretical background, 43-44 observability, 208 quantum theory, 200 Phase-inverting reactions molecular model, 496-499 phase-change rule, pericyclic reactions, 449-450... 

Reactive double-slit model (RDSM), non-adiabatic coupling, Longuet-Higgins phase-based treatment, two-dimensional two-surface system, scattering calculation, 150-155... 

Herzberg-Longuet-Higgins phase, Jahn-Teller model, 185—186... 

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