The quest for fully hydrogen-ordered ice XIV

Water ice displays a remarkably complex phase diagram containing pairs of hydrogen-ordered / disordered phases. Ice XII is a hydrogen-disordered phase and ice XIV is its hydrogen-ordered counterpart, which was discovered by our group. A recent article has claimed that ice XIV can be fully hydrogen-ordered. However, this claim turned out to be the result of an integration error. In fact, only 60% ordering has been achieved so far. Our group has recently investigated the metastability regions of ices XII/XIV towards high pressures. Consistent with our earlier finding that the ice XII to ice XIV transition goes along with a volume decrease, we have found that increasing the pressure facilitates the ordering of ice XIV. We now plan to form ice XIV at the highest possible pressures using the Paris Edinburgh cell with the ultimate goal of preparing the fully ordered ice XIV after all.