The molecular dynamics (MD) simulation employing the embedded atom method (EAM) has been performed to examine the phase stability of Pt nanoclusters, Ptn (n=38, 147, 309 and 561 atoms) with size and temperature. From heating and freezing curves of the nanoclusters,
the clusters (Pt147, Pt309 and Pt561) larger than 1 nm in size showed an icosahedral morphology near 460 ~ 660 K during freezing, where the formation energy of the icosahedral phase is 0.051 eV/atom for Pt147, 0.056eV/atom for Pt309 and 0.067 eV/atom for Pt561. We also investigated coalescence between two Pt nanoclusters and observed that the minimum size of the coalescent one is around 1nm at 673 K.