Bond-correlated percolation model and the unusual behaviour of supercooled water

It is shown that the partition function of an interaction Hamiltonian for the hydrogen bonding in water molecules may be expressed as the generating function of a bond-correlated percolation model with a bond probability p depending on the hydrogen-bond strength and the temperature T. Assuming that the molecules with larger number of active bonds have a larger volume per molecule, one may show that, for temperatures near but higher than the temperature of maximum bond fluctuations, the isothermal compressibility K T and the constant pressure specific heat C p increase, while the thermal expansivity alpha p becomes more negative, as T decreases. Other unusual behaviour of supercooled water can also be explained by this model.