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Huckel theory (Read 4432 times)
Gerrit-Jan Linker
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Huckel theory
17.01.08 at 15:13:43
 
Huckel theory
 
In Huckel MO (HMO) theory only the outermost p electrons are taken into consideration. For conjugated pi systems where the p electrons are quite separated from the core electrons this is a reasonable approximation. Further, in Huckel theory only the resonance integrals, beta between neighbor atoms are used in addition to the coulomb integrals, alpha.
 
Characteristics:

  • Applicable to conjugated hydrocarbons
  • Only pi electron MO's are included, sigma MO's are not included
  • It expresses MO energies in terms of alpha (the energy of a p electron) and beta (the interaction energy of adjecent p electrons).

 
For an explanation of the theory see:
http://chemistry.umeche.maine.edu/Modeling/lcao.html
http://en.wikipedia.org/wiki/Hückel_method
 
http://www.jce.divched.org/jcedlib/livtexts/pchem/jce2005p1880_2ltxt/quantumstat es/Bookfolder/L21Huckel_MO_Theory.htm
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« Last Edit: 21.12.11 at 09:24:56 by Gerrit-Jan Linker »  

Gerrit-Jan Linker
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Gerrit-Jan Linker
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Posts: 75
Extended Huckel theory
Reply #1 - 06.06.10 at 21:41:35
 
Extended Huckel theory
 
The extended Hückel method is a semiempirical quantum chemistry method s based on the Hückel method but, while the original Hückel method only considers pi orbitals, the extended method also includes the sigma orbitals.
 
source:
http://en.wikipedia.org/wiki/Extended_Huckel_method
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Gerrit-Jan Linker
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