The UHF Green's Function Method for Molecular Electronic Structures

Abstract

The Green's function method has been applied to molecular electronic system with closed shell structure or to RHF state. In this article, the Green's function technique is extended to the framework of UHF theory for molecular electronic system. For simplicity, the UHF scheme is interpreted in the view point of LCAO MO method. In order to represent the UHF state by the Green's function method, the extension is made for the definition of one­ body Green's function. The spin and charge densities are given with the perturbation calculation starting from the UHF one. To compute the excitation energies of an electronic ,.;ystem, the particle-hole two-body Green's function is also introduced and the RPA equation for the UHF state is obtained. As an example for the UHF Green's function method, applications are made for the pi-electron system of an allyl-radical.