Phase relations for water and ice in confined geometry

A brief survey is given of the structural characteristics of water at low temperatures in the normal and super-cooled states using neutron diffraction. Similar studies axe presented for D2O water in mesoporous sol-gel silicas showing the depression of the nucleation temperature, the effects of fractional filling and the formation of cubic ice I-c in the pores. Preliminary data is also presented for both neutron and x-ray diffraction studies of water in the ordered MCM41 silica, showing the deep super-cooling and the reversible phase transformation between water and cubic ice. The importance of hydrogen-bonded networks and the development of long-range correlations axe used to provide an explanation of the observations. Further work is in progress.