Raman spectroscopic features of hydrogen-ordering in ice XII

The Raman spectra of recovered hydrogen ordered H2O and D2O ice XIV were recorded and compared with the spectra of the corresponding hydrogen disordered phase (ice XII). On heating ice XIV, the transition to ice XII is observed. Subsequent cooling leads to the weak reappearance of ice XIV lattice vibrational peaks which demonstrates the reversibility of the hydrogen order ↔ disorder phase transition. However, cooling at ambient pressure produces a less ordered ice XIV than cooling under pressure which implies that pressure favours hydrogen ordering of ice XII.