The electronic states of Fe 2

The equilibrium bond lengths, harmonic vibrational frequencies, ionization energies and dissociation energies of the iron dimer and its cation were determined by hybrid density functional theory calculations supplemented by single point calculations using coupled cluster theory. Calculations predict correctly the 9 Σ g − state as the ground state of Fe 2. The ionization and dissociation energies have been found to compare satisfactorily with the experimental values. The ground state of Fe 2 + is found to be 10 Σ g − , corresponding to the 3d 124s 3 valence electronic configuration. However, it is worth mentioning that the 8 Σ u + state (3d 134s 2) is calculated to lie only 0.14 eV higher in energy.