Phase stability of Pt nanoclusters and the effect of a (0 0 0 1) graphite surface through molecular dynamics simulation

A molecular dynamics (MD) simulation with an embedded atom scheme (EAM) is used to investigate the phase stability of Ptn (n = 38, 147, 309 and 561 atoms) nanoclusters under various temperature conditions. The heating and freezing behaviors show that the Pt147, Pt309 and Pt561 clusters have icosahedral morphologies in the temperature range of 460-660 K during freezing, where their formation energies are 0.051 eV/atom for Pt147, 0.056 eV/atom for Pt309, and 0.067 eV/atom for Pt561. The calculation of the free energy change, which is based on the Gibbs-Thomson effect, implies that the coalescence phenomenon of the nanoclusters is a thermodynamically stable process. On a (0 0 0 1) graphite surface, the bottom layer of a Pt nanocluster is rearranged to a close-packed plane due to the arrangements of carbon atoms on the graphite surface, and this rearrangement disturbs the formation of a spherical Pt cluster.