The structure of Ni-46, Ni-47, and Ni-48

The geometrical structures of Ni-46, Ni-47, and Ni-48 are investigated by t he chemical probe method using molecular nitrogen as the probe molecule. Ni trogen saturation levels are determined and found to be consistent with clu ster structures derived from two geometries, one having face-centered-cubic (fcc) packing and the other fcc/hcp (hexagonal-close-packed) layered packi ng. The fcc-based structures provide the best overall agreement with the ex perimental measurements. The saturation levels are inconsistent with icosah edral or decahedral packing, a structure found for Ni-49 and larger cluster s in earlier experiments. The change in cluster structure between Ni-48 and Ni-49 (most likely from fcc to icosahedral packing) is clearly evident in the nitrogen adsorption experiments at both low and high coverages, as well as with other reagent molecules. (C) 2001 American Institute of Physics.