Chemical Bonding, Electron Affinity, and Ionization Energies of the Homonuclear 3d Metal Dimers

Abstract

Electronic and geometrical structures of the homonuclear 3d metal dimers M2 (from Sc2 to Zn2) as well as their anions and cations are computed using density functional theory with six generalized gradient approximations for the exchange-correlation potential. The neutral ground states are assigned as follows: Sc2 (5 ), Ti2 (3Δg), V2 (3 ), Cr2 (1Σ+), Mn2 (11Πu), Fe2 (7Δu), Co2 (5Δg), Ni2 (3 ), Cu2 (1 ), and Zn2 (1 ). The anions are assigned as follows: (4 ), (4Δu), (4 ), (2Σ+), (10 ), (8Δg), (6Δu), (4 ), and (2 ) ( is unbound). The cations ground states are: (4 ), (2Δg), (4 ), (2Σ+), (10Πu), (8Δu), (6Γg), (4Δg), (2 ), and (2 ). A natural bond (NBO) analysis is used to obtain the chemical bonding patterns in the neutral and charged dimers. The results of the NBO analysis allow us to explain the changes in the ground-state spin multiplicities and spatial symmetries when moving along the neutral and ionic series. Consistent changes in the chemical bonding patterns of the neutral and charged dimers lend further support to our assignment of the ground states in the and series. Our calculated adiabatic electron affinities and ionization energies are in good agreement with experiment.