The zero-point energy of the unusual ice II phase

Water displays a highly complex phase diagram that is key to a range of critical processes, from the evolution of icy moons to that of the Earth's hydrosphere and even of life itself. Using ISIS facilities, we have recently shown that the water phase diagram is hypersensitive to ammonium fluoride doping which leads to the complete disappearance of the hydrogen-ordered ice II from the phase diagram. This phenomenon can be explained on the basis of the topologically constraint nature of ice II and the incompatibility of ammonium and fluoride ions with the ordered local structure. Consistent with our findings, it has been shown computationally that ice II has an unusually low zero-point energy. This is what we would now like to test experimentally using DINS measurements on the VESUVIO instrument. These experiments will give new insights into the origins of the complexity of condensed H2O.