Medium-density amorphous ice.

Rosu-Finsen, Alexander; Davies, Michael B; Amon, Alfred; Wu, Han; Sella, Andrea; Michaelides, Angelos; Salzmann, Christoph G · Science · 2023

basic_science · Level V

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Abstract

Amorphous ices govern a range of cosmological processes and are potentially key materials for explaining the anomalies of liquid water. A substantial density gap between low-density and high-density amorphous ice with liquid water in the middle is a cornerstone of our current understanding of water. However, we show that ball milling "ordinary" ice I<i>h</i> at low temperature gives a structurally distinct medium-density amorphous ice (MDA) within this density gap. These results raise the possibility that MDA is the true glassy state of liquid water or alternatively a heavily sheared crystalline state. Notably, the compression of MDA at low temperature leads to a sharp increase of its recrystallization enthalpy, highlighting that H<sub>2</sub>O can be a high-energy geophysical material.