The everlasting hunt for new ice phases

Abstract

Water ice exists in hugely different environments, artificially or naturally occurring ones across the universe. The phase diagram of crystalline phases of ice is still under construction: a high-pressure phase, ice XIX, has just been reported but its structure remains ambiguous.

Fig. 1. Schematic phase diagram of crystalline ice phases inspired by Bartels-Rausch et al., Salzmann et al. and Huang et al..

Phases labeled with black Roman numerals are hydrogen-disordered phases; those labeled with red numerals are hydrogen-ordered phases; those labeled with blue numerals are metastable phases. The red solid arrows represent direct disorder-order transitions. The red dotted arrows represent disorder-order transitions that cross the stability range of another phase.