Electronic Resource
College Park, Md.
:
American Institute of Physics (AIP)
The Journal of Chemical Physics
90 (1989), S. 2741-2751
ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
We contrast a simple molecular orbital theory (Hückel) with a simple valence bond theory (Heisenberg–Dirac). We find for alternant systems in which both models have nondegenerate ground states that both models have ground states belonging to the most symmetrical irreducible representation of the molecular point group. We also find there exist nonalternant systems which have ground states with different irreducible representations. In these latter systems neither the Hückel nor the Heisenberg–Dirac model is sufficient to give a qualitative picture of the molecule. Instead a combined Hückel–Heisenberg–Dirac model (the Hubbard model) must be used. Finally we list some organic unsaturated hydrocarbons, whose ground state changes from one irreducible representation to another as the Hubbard parameters vary.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.455921
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