Structure and energetics of Ni, Ag, and Au nanoclusters

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Abstract
The geometries and binding energies of the most stable isomers of nickel, silver, and gold nanoclusters of size 6, 7, 12, 13, 14, 19, 38, 55, and 75 atoms, predicted with an n-body Gupta potential, are presented. An exhaustive search for low-energy minima on the potential energy surface was carried out using an evolutive (genetic-symbiotic) algorithm. Our results confirm the existence of disordered global minima for gold clusters of 19, 38, and 55 atoms in size, and disordered low-energy isomers for the 75-atom gold cluster. Disordered structures are also isomers of nickel and silver clusters but they are not among the global minima of these metals. Comparison of the structure factors of the disordered and ordered isomers of gold with published experimental x-ray powder diffraction data suggests that the disordered structures are real. The relation between the form of the n-body potential and the structure of the global minimum is studied, leading to an explanation of why these disordered states were located with the Gupta potential but not with certain other models of the metal bonding.