The change of the structural and thermodynamic properties of water from ambient to supercritical conditions as seen by computer simulations

Results of Monte Carlo simulations with various polarizable potential model s and reverse Monte Carlo simulations of water are reported at different th ermodynamic state points from ambient to supercritical conditions. It is sh own that polarizable potential models can reproduce the change of the exper imental partial pair correlation functions of water with the temperature an d density considerably better than simple nonpolarizable models. Thus, for instance, only the polarizable models can reproduce the experimentally obse rved elongation of the hydrogen bonds with increasing temperature and decre asing density. On the other hand, the densities of the polarizable water mo dels decrease unexpectedly fast with increasing temperature, which affects also the reproduction of other thermodynamic properties at states of high p ressure and high temperature. In analysing the properties of the hydrogen b onded clusters it is found that the space-filling percolating network of th e molecules breaks down around the critical point, although a large number of hydrogen bonds still remain in the system above the critical point.