Electronic Structure and Nature of Bonding in Transition Metal Dimers

Abstract

All electron ab initio Hartree-Fock and configuration interaction methods have been applied to elucidate the electronic structure and the nature of bonding of the transition metal dimers Cu2, Ni2, Co2, Fe2, Ag2, Pd2, Rh2, Nb2. Towards the end of the transition metal series the d electrons tend to localize around the nuclei, and they therefore participate only slightly in the bond formation. However, due to the various exchange couplings the d electrons give rise to large numbers of extremely close-lying potential energy curves. Towards the middle of the transition metal series the d electron participation in bond formation appears as larger populations in the bonding natural orbital relative to the antibonding natural orbitals. The chemical bonds of all the molecules considered are very complicated, and even when the d electrons participate significantly in the bond formation the molecular orbital picture is inadequate for describing the bonds.