ROLE OF HYDROGEN-BOND COOPERATIVITY AND FREE-VOLUME FLUCTUATIONS IN THE NON-ARRHENIUS BEHAVIOR OF WATER SELF-DIFFUSION - A CONTINUITY-OF-STATES MODEL

Some thermodynamic and transport properties of normal and supercooled water have been interpreted in the framework of a dynamic extension of the polychromatic percolation model in which both the recently report ed evidence for a temperature-dependent H-bond cooperativity and free- volume fluctuations within the percolative patches are included. The p roposed model, which allowed us to fit the experimental self-diffusion data as a function of the temperature to an accuracy comparable to th at obtained by a power law, is consistent with the existence of a cont inuity of states between liquid and solid phases, rather than being in dicative of the presence of singularities in the supercooled region.