EFFECT OF POTENTIAL-ENERGY TOPOGRAPHY ON DYNAMICS AND PHASE-BEHAVIOR OF CLUSTERS

Clusters of seven identical particles, bound by pairwise Morse potenti als, simulated at constant energy, exhibit zones of dynamic coexistenc e of solid-like and liquid-like forms if the range parameter rho(0) = beta r(0) of the potential is large, corresponding to a short-range pa ir interaction. However no such phase coexistence occurs for longer-ra nge Morse potentials, according to the criterion of bimodality (or uni modality, for no coexistence) of the distribution of short-time averag e vibrational temperatures. The difference is due to the smoother topo graphy of the multidimensional potential surface generated by the long er-range pair potentials, particularly in the higher-energy reaches of that surface.