Stable structures of neutral and charged iron clusters by self-consistent tight-binding molecular-dynamics

By using the simulated-annealing technique with a tight-binding molecular-dynamics, fully optimized structures of iron clusters are determined for the number of atoms, n = 2-17. It is found that the clusters with sizes, n = 6, 7, and 13, are relatively stable. Iron clusters show an icosahedral growth similar to rare gas clusters. HOMO-LUMO energy gaps are calculated, and electronic shell effects are absent. Additionally, by performing a self-consistent tight-binding molecular-dynamics calculations, we obtain fully optimized structures of positively- and negatively-charged iron clusters. Nearest-neighbor distance of positively- and negatively-charged iron clusters reveals an decrement and increment compared to that of the neutral clusters, respectively. These changes in the interatomic distances are mainly due to the changes in the number of HOMO electrons in anti-bonding molecular-orbitals.