Advances in the experimental exploration of water's phase diagram

TL;DR

This paper reviews recent experimental advances in understanding water's complex phase diagram, highlighting new findings on ice polymorphs, phase transitions, and the influence of chemical doping, marking an exciting era in ice research.

Contribution

It provides a comprehensive overview of recent experimental progress and discusses open questions and future challenges in water's phase diagram research.

Findings

Discovery of new low-density ice polymorphs

Insights into pressure amorphization mechanisms

Effects of chemical doping on phase transitions

Abstract

Water's phase diagram displays enormous complexity with currently 17 experimentally-confirmed polymorphs of ice and several more predicted computationally. For almost 120 years, it has been a stomping ground for scientific discovery and ice research has often been a trailblazer for investigations into a wide range of materials-related phenomena. Here, the experimental progress of the last couple of years is reviewed, and open questions as well as future challenges are discussed. The specific topics include the polytypism and stacking disorder of ice I, the mechanism of the pressure amorphization of ice I, the emptying of gas-filled clathrate hydrates to give new low-density ice polymorphs, the effects of acid / base doping on hydrogen-ordering phase transitions as well as the formation of solids solutions between salts and the ice polymorphs, and the effect this has on the appearance of the phase diagram. In addition to continuing efforts to push the boundaries in terms of the extremes of pressure and temperature, the exploration of the 'chemical' dimensions of ice research appears to now be a newly emerging trend. It is without question that ice research has entered a very exciting era.