Detailed crystallographic analysis of the ice V to ice XIII hydrogen-ordering phase transition

Ice V is a structurally highly complex material with 28 water molecules in its monoclinic unit cell. It classified as hydrogen-disordered phase of ice. Yet, some hydrogen-bonded display significant orientational order. Upon cooling pure ice V, additional ordering cannot be achieved on the experimental time scale. Doping hydrochloric acid has been shown to most effective enabling transition hydrogen-ordered counterpart XIII. Here, we present detailed crystallographic study this investigating effects and hydrofluoric well lithium potassium hydroxide doping. The magnitudes stepwise changes lattice constants during are found more sensitive indicators for extent hydrogen order XIII than appearance new Bragg peaks. Hydrofluoric doping enable similar processes but slower kinetics. various possible space groups ordered configurations examined systematically, previously determined P21/a structure confirmed. Interestingly, partial already perpetuate into XIII, these independent pressure. Overall, goes along small increase volume, which appears origin hydrogen-ordering kinetics under Heating pressure-quenched samples at ambient pressure revealed low-temperature “transient ordering” features both diffraction calorimetry.