Molecular orbital method Coulomb integrals

It is possible to derive instructive information concerning the general features of the electronic structure of a bond systems by making drastic assumptions on the value of the parameters a and fi. First, one obtains a bond orbital scheme if all resonance integrals between hybrids not involved in a chemical bond jure set equal to zero consequently, the delocalization effects can be treated by the standard perturbation theory of the molecular-orbital method second, if all the Coulomb integrals are... 

The U s can in the molecular orbital method (Hiickel approximation) be easily expressed in terms of Coulomb integrals a and resonance integrals which characterize the C atoms and the CC bonds.39... 

In this method molecular orbitals are constructed from a set of basis orbitals represented by the valence orbitals of the atoms in the molecule, i.e. 2 s and 2p for first TOW elements, 3 d, 4 s, and 4p functions for the transition elements, and the 1 s orbital for hydrogen. The one-electron elements are represented by an average of the ionisation energy and the electron affinity of the orbital, while all two-electron integrals are n ected with the exception of one- and two-centre coulomb type terms and one-centre exchange integrals. Calculations were performed in the unrestricted Hartree-Fock formalism using the matrix elements —... 

This section deals with analytical properties of the Hiickel molecular orbital theory and the associated isolated molecule method of predicting the active positions in a conjugated molecule. We shall deal with polarizability coefficients defined as certain partial derivatives with respect to the coulomb and resonance integrals described in Section III. The important derivatives are those relating to the total tt electron energy and to the charges q, fi ee valences and bond orders... 

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