COOPERATIVITY AND HYDROGEN-BOND NETWORK LIFETIME IN LIQUID WATER

The lifetime of the H bond network has been calculated as a function o f temperature by a statistical five-species model for water in which t he H bond cooperativity has been explicitly taken into account. While, on one hand, the Arrhenius behavior of the depolarized Rayleigh scatt ering data existing in an intermediate temperature region is well repr oduced, the model predicts that the H bond lifetime diverges as the su percooled temperature limit is approached. The observed cooperative st abilization of the H bonds in tetracoordinated molecules occurring in the deep supercooled region, where this species becomes the most long- lived one, points out the tendency of the system to unavoidably approa ch ice rather than to reach a region of dynamical instability.