The Ising model of confined water in CNT

Abstract

The Ising model, describing mathematically phase transitions between disordered and ordered states in ferromagnets and binary alloys, has been applied to the freezing process of water confined inside the carbon nanotube. To take into account the rearrangement of water molecules inside the carbon nanotube to retain their hydrogen bonds in competition with van der Waals interactions with carbon atoms of the nanotube, an additional term has been introduced into the formula for the ordering parameter in water. Inclusion of this hydrophobic effect which depends exponentially upon the diameter of the tube within the Ising model yields an expression for the dependence of freezing temperature of water inside the CNT upon its diameter. According to the model, the smaller the diameter of the tube, the higher freezing temperature of water molecules. These theoretical results are in a good agreement with the experimental data.