A scheme for obtaining approximate solutions of the electronic Schrouml;dinger equation is proposed in terms of an extended group function model. The model is formulated within the context of the method of moments. The model is size consistent, and it has additive accuracy since the correction to a pure antisymmetrized product function is obtained as additive terms describing intragroup and intergroup correlation corrections. In a test calculation on the ground state potential energy curve for the F2molecule, the advocated model yields a dissociation energy of 1.63(1.66) eV and an equilibrium internuclear distance of 1.392(1.412) Aring;. Experimental values are within parenthesis.
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