We find that the potential energy distribution of atoms in clusters can consistently explain many important
phenomena related to the phase changes of clusters, such as the nonmonotonic variation of melting
temperature with size, the dependence of melting, boiling, and sublimation temperatures on the interatomic
potentials, the existence of a surface-melted phase, and the absence of a premelting peak in heat
capacity curves. We also find a new type of premelting mechanism in double icosahedral Pd19 clusters,
where one of the two internal atoms escapes to the surface at the premelting temperature.