NEUTRON DIFFRACTION STUDIES OF WATER IN AMBIENT, SUPER-COOLED AND AMORPHOUS STATES

The structure of liquid water in the stable and metastable phases is dominated by the orientational effects of hydrogen-bonding on the local molecular environment. As the temperature is reduced the hydrogen-bond connectivity is increased and the structural features of the super-cooled state appear to be evolving towards the continuous random network structure of low-density amorphous ice. The use of neutron diffraction techniques for the study of liquid water and amorphous ice shows how the variation in the orientational correlations influences the properties. Water has a delicate structure which is sensitive to various external parameters such as temperature and/or pressure which can be understood in terms of the hydrogen-bond connectivity. The presence of apolar atoms in this environment perturbs this network and recent studies have shown how the water molecules can form clathrate type cages around the isolated atom.