Structure and Properties of Fen, Fen–, and Fen+ Clusters, n = 7–20

The electronic and geometrical structures of the Fen, Fen–, and Fen+ series (n = 7–20) are studied using all-electron density functional theory with the generalized gradient approximation. Equilibria of the geometrical configurations of the lowest total energy states in all three series are found to be similar except for Fe9–, Fe9+, Fe10–, Fe10+, Fe15–, and Fe19+. Our computed ionization energies of the neutrals, vertical electron detachment energies, and energies of Fe atom abstraction are in good agreement with experiment. It is found that the one-electron model corresponding to the change in the total magnetic moment of ±1.0μB due to either attachment or detachment of an electron is valid in most cases. The exceptions are Fe4+, Fe10–, Fe10+, Fe12–, Fe13+, and Fe14+, where the change in the total magnetic moment is +3μB (Fe10– and Fe12–), −3μB (Fe4+, Fe11+, and Fe14+), and −9μB (Fe13+). The reason for an anomalously large quenching of the total spin magnetic moment in Fe13+ is explained. Our computed total spin magnetic moments per atom match the recent experimental values within the experimental uncertainty bars.