Generalized Mo/ller–Plesset and Epstein–Nesbet perturbation theory applied to multiply bonded molecules

Abstract

A generalized Mo/ller–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 Mo/ller–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 multiconfigurational 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.