  The first order phase transition of a water cluster confined in a dynamic
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 on determining the
dependence of transition temperature on the nanotube diameter.
