Melting behaviors of icosahedral metal clusters studied by Monte Carlo simulations.

We present an atom-resolved analysis method that traces physical quantities such as the root-mean-square bond length fluctuation and coordination number for individual atoms as functions of temperature or time. This method is applied to explain the temperature-dependent behaviors of three types of Ni-N (N = 12, 13, 14) clusters. The detailed studies for the three types of clusters reveal characteristics as follows: (a) as the temperature increases, all three types of clusters undergo two-stage melting, irrespective of the existence of vacancy or adatom on the icosahedral surfaces, (b) the melting of icosahedral clusters with vacancy starts with vacancy hopping, which has not been observed for any type of small clusters (N < 34), (c) the melting of the icosahedral clusters with adatom (N = 14) is initiated by adatom hopping, followed by the site exchange between the adatom and surface atoms. (C) 2000 John Wiley & Sons, Inc.