Statistical mechanics of hydrogen bond networks

The static and dynamic properties of several hydrogen bond network models, based on thesquare ice model of Lieb Phys. Rev.162, 162 (1967)] are studied. The two dimensionalsquare water (SW) model and the three-dimensioaalbrick water (BW) model were analyzed by means of Monte Carlo simulations. A simplified vesion of SW (simplified square water, SSW) can be solved exactly. All models yield similar thermodynamic results which can be derived-alternatively-from an independent bond approach due to Angell J. Chem. Phys.75, 3698 (1971)]. We suggest the existence of a universality class of hydrogen bond networks that can be described by this theory, and which may include the liquid state of water. The mean lifetime of a hydrogen bond exhibits an Arrhenius temperature dependence. Comparison with experimental data on water provides an absolute time scale for the Monte Carlo simulations. The possible use of these models in simulations of protein-solvent systems is discussed.