Size-temperature phase diagram for small Lennard-Jones clusters.

The size-temperature "phase diagram" for small Lennard-Jones clusters LJn (n< or =147) is constructed based on the analysis of the heat capacities Cv(T) , computed by the parallel tempering Monte Carlo method. Two types of "phase transitions" are often observed: the higher-temperature solid-liquid transition, due to melting of the cluster core, and the lower-temperature melting that occurs within the surface layer. The latter transition can only be observed for clusters with Mackay packing of the overlayer.