The effects of nitrogen on the configurations and magnetic moments of small iron, cobalt and nickel clusters

Abstract

The configurations, electronic structures and magnetic properties for M n N clusters ( M = Fe, Co, Ni; n = 2−12, 14, 18) are obtained using all-electron density functional theory calculations at the general gradient approximation level. On doping an N atom into the pure M n clusters, the ground-state structures, binding energies of the resulting mixed clusters have changed but the average M – M bond length does not obviously change except for Fe 2 N, Co 7 N and Ni 7 N. The doping N atom prefers surface sites except for n = 14 and 18. The results also show the enhanced stability for M n N clusters compared with that of the corresponding pure M n clusters. The large energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital for Fe n N ( n = 6,12), Co n N ( n = 3,5,7,9,11) and Ni n N ( n = 3,6,11,14) clusters indicate their high chemical inertness. Moreover, it has also been found that the total spin magnetic moments of all the M atoms increase slightly for: M = Fe, n = 9,12,14; M = Co, n = 8,9,11,18; and M = Ni, n = 3,11,12.