Elementary Excitations in a Benzene Model

A two-parameter model for the π electrons in the benzene molecule is examined in detail by the method of complete configuration interaction and the results are used for a comparison with an approximate propagator or Green's function technique applied to the model. It is demonstrated that the approximate method gives a qualitatively nearly correct description of the electronic structure for a range of parameter values which simulate the limits of separated atoms and of small electronic interaction. The quantitative comparison is generally better than what is possible with the molecular orbital method.