phases of ice come in pairs

To date, fifteen phases of ice have been discovered. Equilibrium phases are shown below on the left, while on the right, some metastable phases, which will eventually revert to an equilibrium phase, are added. Twelve of these phases occur in pairs consisting of a hydrogen bond disordered phase and a lower-temperature ordered phase: Ih and XI, III and IX, V and XIII, VII and VIII and XII and XIV.

phases of ice

h-bonds in ice Ih The disordered phase contains the water oxygens in nearly the same positions as the fully ordered phase, but the orientations of hydrogens are disordered. The animation on the right shows the origin of the hydrogen bond disorder. You can see that many different unit cells of ice can be built in which each water is fully satisfied with four hydrogen bonds.

Our research examines the phase transitions between members of these ordered/disordered pairs.  We have successfully predicted 5 of the 6 transitions, and experiments are still underway for the last one.  We have predicted how local hydrogen bond disorder can account for small shifts of the waters from the average positions.  We have also examined the behavior of charged defects, like H+ and OH- in ice.

This research has been supported by the National Science Foundation.

some relevant publications