Embedded atom calculations of the equilibrium shape of small platinum clusters

The embedded atom method was used to examine the shapes and stability of a series of platinum clusters with 5-60 atoms. The calculations suggest that the polyhedral structures seen in previous calculations are not stable. While the magic-number icosahedrons,cubo-octahedrons, tetrahedrons, and octahedrons retain their shape at 0 K, they spontaneously reconstruct upon annealing to 300 K. The nonmagic-number truncated icosahedrons, cubo-octahedrons, tetrahedrons, and octahedrons spontaneously reconstruct even at 0 K. A 147-atom icosahedron was also found to reconstruct to a lower energy structure upon annealing to 500 K. In contrast, there are a series of lower energy structures which are reasonably stable at 100-300 K. These lower energy structures are highly disordered and show surface structures which are not present in bulk platinum. At this point the calculations have not yet considered the effects of the support. However, these results suggest that small platinum clusters may be much more disordered than previous calculations suggest.