Physical picture of electron correlations in three-center four-electron bonds

Abstract

It is shown that the strong electron correlations of π electrons in the O3 molecule may be well understood in terms of a simple analytic model which is a natural extension of a bond orbital approximation to the case of a three-center bond. Electron correlations are here responsible for the increase of density at the central atom and for enhanced correlations at both terminal ones. This result is confirmed by a numerical calculation of the interatomic correlations by using a local ansatz imposed on a semiempirical selfconsistent field ground state. It is argued that the discussed increase of the bond polarity in the O3 molecule is a universal phenomenon for three-center bonds filled (on the average) by more than one electron per atom, as, for example within the CuO2 planes of Cu based perovskites.