Connection between liquid and glassy states in water

In water, the existence of at least two different forms of glass, i.e., the low-density amorphous (LDA) and the high-density amorphous (HDA) ices, and of one anomalous liquid, points to a hidden connection between these states, whose understanding has the potential to shed light on the complex nature of water’s behavior. Here, we develop a Neural Network scheme capable of discerning local structures beyond tetrahedrality. Applied over a wide region of the water’s phase diagram, we show that the local structures that characterize both LDA and HDA amorphous phases are indeed embedded in the supercooled liquid phase. Remarkably, the rapid increase in the LDA-like population with supercooling occurs in the same temperature and pressure region where thermodynamic fluctuations are maximized, linking these structures with water’s anomalies. At the same time, the population of HDA-like environments rapidly increases with pressure, becoming the majority component at high density. Our results show that both LDA and HDA are genuine glasses, and provide a microscopic connection between the non-equilibrium and equilibrium phase diagrams of water.

F.Martelli, F.Leoni, F.Sciortino, J.Russo "Connection between liquid and non-crystalline solid phases in water" J. Chem. Phys. 153, 104503 (2020)