Molecular dynamics of ice-nanotube formation inside carbon nanotubes

The phase transition of a water cluster confined in a flexible single-walled carbon nanotube is investigated using a classical molecular dynamics (MD) method. The formation of ice-nanotube is monitored through the structure factor and potential energies. The transition temperature and its diameter dependence obtained by the simulations agree well with those of previously reported experiments. The transition temperature of the ice-nanotube was shown to take a maximum value of around room temperature with the number of the ring members n = 5. Potential energy contribution to the phase change is generally dominated by that of the intrinsic water-water interaction, while that of water-carbon interaction plays a significant role in determining the dependence of transition temperature on the nanotube diameter.