Quantum phase transition of water clusters: molecular dynamics simulations with a model potential

We have performed molecular dynamics (MD) simulations on water octamer clusters with a model potential (SPC/F-2). In addition to classical MD simulations, path integral MD simulations are performed to study quantum effects in the phase transitions of the system. Replica exchange method is used for efficient canonical samplings. Order parameters at various temperatures are calculated by classical and quantum simulations, respectively. It is found that the cluster exhibits quantum behavior in phase transitions around 100 K. The phase transition temperature is found to be lower by 25 K for quantum simulations, compared to the classical simulations. (C) 2004 Elsevier B.V. All rights reserved.