Geometry and electronic structures of magic transition-metal oxide clusters M9O6 (M = Fe, Co, and Ni)

The magic oxide clusters M9O6 (M = Fe, Co, Ni) are found by using reactive laser vaporized cluster source. From the first-principles calculations, the possible equilibrium geometries for these three oxide clusters are determined to be a C-2 nu symmetry, where the skeleton composed of 9 metal atoms also has C2(nu) symmetry, different from the equilibrium structures of pure transition metal cluster M-9. The O atoms are energetically more favorable to cap the triangle surfaces. In Fe9O6 and Co9O6 clusters, oxygen atoms are antiferromagnetically polarized while ferromagnetically polarized in the Ni9O6 cluster, Similar to the case of O atoms adsorbed on the reconstructed Ni(110) surface. The magnetic behaviors are explained from electronic structures.