The relevance of models
describing molecular electronic energies including electrostatic as well as
covalence effects is outlined and a summary of developments resulting in the
present formulation is given. A simple, semi-empirical model based on a LCAO-MO
approximation and comprising the point charge electrostatic model and angular
overlap model is formulated. Although the present formulation is restricted to
the antibonding effects of covalence it is applicable to p, d, f and g orbital
energies. The mathematical and conceptual simplicity of the model derives from
the application of a re-parameterized ionic model and the superposition
principle for ligand contributions, the latter applied in the case of ionic as
well as antibonding effects. A physical interpretation of the model, for
diatomic as well as polyatomic molecules, is presented and the results of its
application to the pentachlorovanadate(IV) ion are cited.
On the Parameterization in the Semi-Empirical LCAO MO Method