GENERALIZED MOLLER-PLESSET AND EPSTEIN-NESBET PERTURBATION-THEORY APPLIED TO MULTIPLY BONDED MOLECULES

A generalized Moller-Plesset theory based upon a multiconfigurational reference wave function is applied to the problem of the dissociation of multiple bonds, in particular, to the molecules N2, C2H2, O2++, and C2H4. The second order generalized Moller-Plesset theory is shown to be nearly as accurate as corresponding multireference configuration interaction (CI) calculations with less computational effort. An analysis is given of the size of the multi-configurational reference necessary for a perturbative treatment of the dissociation of multiple bonds. The relative merits of the computationally simpler multiconfigurational Epstein-Nesbet perturbation theory are presented.