Theoretical study of the electronic structure of the transition metal dimers, Sc2, Cr2, Mo2 and Ni2

Abstract

MCSCF calculations of the potential energy curves of the ground states of the transition metal species Sc₂, Cr₂, Mo₂ and Ni₂ are described. The ground state of Sc₂ is calculated to be ⁵∑^–_u, corresponding to the orbital occupancy σ²_g(s)σ¹_g(d)π²_u(d)σ¹_u(s). In Ni₂ the metal–metal bonding is due to the doubly occupied σ_g(s) orbital, a number of very closely spaced states arising from the weakly interacting pair of nickel d⁹ configurations. In Cr₂ and Mo₂ a major feature of the bonding is the reduction in the order of the “sextuple” bond due to correlation effects, particularly in Cr₂. Binding energies of all four diatomic species are calculated and compared with available experimental data.