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 numb er for individual atoms as functions of temperature or time. This method is applied to explain the temperature-dependent behaviors of three types of N i-N (N = 12, 13, 14) clusters. The detailed studies for the three types of clusters reveal characteristics as follows: (a) as the temperature increase s, all three types of clusters undergo two-stage melting, irrespective of t he existence of vacancy or adatom on the icosahedral surfaces, (b) the melt ing of icosahedral clusters with vacancy starts with vacancy hopping, which has not been observed for any type of small clusters (N < 34), (c) the mel ting of the icosahedral clusters with adatom (N = 14) is initiated by adato m hopping, followed by the site exchange between the adatom and surface ato ms. (C) 2000 John Wiley & Sons, Inc.