  Using molecular dynamics simulation technique, we have studied the melting
behaviours of free, icosahedral PtN clusters in the size range of N=12-14.
Voter and Chen version of an embedded-atom model, derived by fitting to
experimental data of both diatomic molecule and bulk platinum simultaneously,
has been employed in the study. We present an atom-resolved analysis method
that includes physical quantities such as the root-mean-square bond-length
fluctuation and coordination number for individual atoms as functions of
temperature. The results show that while 13-atom icosahedron and 12-atom
cluster with a vacancy on the icosahedral surface exhibit one-stage melting,
14-atom cluster with an adatom on the icosahedral surface undergoes two-stage
melting, as the temperature increases.
