Abstract
Molecular dynamics simulations were performed to investigate the phase change of a water cluster confined in a single-walled carbon nanotube. The first order phase transition of the water cluster to an ice-nanotube is investigated in terms of the dependence of the freezing temperature on the diameter of the carbon nanotube. The simulation aims to validate the experimental observation of the anomalous tube-diameter dependence with opposite trend from that of bulk water in a capillary tube. As a consequence, the calculated freezing temperature agrees well with those measured in experiments. It is shown that the freezing temperature exhibits a maximum value, about room temperature, for nanotube diameter of d=1.1nm, where the ice-nanotube consists of 5-membered rings. Analyses of the potential energy indicate that the freezing temperature is mainly determined by the structural stability of the ice crystal.
