Structural transitions in small molecular clusters

摘要

Clusters of octahedral molecules mimicking TeF_6 afford a vehicle to investigate the analog in small clusters of structural phase transitions through molecular dynamics simulations. Three phaselike forms occur for the solid clusters, both closed-shell structures of 51, 89, and 137 molecules, and open-shell structures of 50, 81, and 129 molecules. The indications are that the free energy has at least two minima as a function of the order parameters. However, whether these converge to a single minimum as N, the number of molecules in the cluster, grows large, leading to a second-order transition in the bulk, or remain apart, implying at least a weak first-order transition in the bulk limit, cannot be determined from the simulations.