The electronic states of Fe2+

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 9Σg− state as the ground state of Fe2. The ionization and dissociation energies have been found to compare satisfactorily with the experimental values. The ground state of Fe2+ is found to be 10Σg−, corresponding to the 3d124s3 valence electronic configuration. However, it is worth mentioning that the 8Σu+ state (3d134s2) is calculated to lie only 0.14 eV higher in energy.