The large-scale structure of amorphous ices and the anomalies of water

by Prof. Roberto Car (Princeton University, USA and Department of Physics, Sapienza University of Rome, cattedra Enrico Fermi)

Tuesday 23 May 2017, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dipartimento di Fisica - Ed. G.Marconi)

Liquid water is often called the most anomalous liquid because its thermodynamic properties depend on temperature in a way that is in marked contrast with the behavior of simple liquids. The anomalies become more pronounced upon cooling. At deeply undercooled conditions, water exhibits polyamorphism, namely it exists in more than one amorphous form, such as the low-density amorphous (LDA) and the high-density amorphous (HDA) ices. Here I will present the results of a recent simulation study of the large-scale structure of LDA and HDA, showing that these systems are nearly hyperuniform, i.e. they possess a "hidden" long-range order that manifests itself in the suppression of large-scale density fluctuations. This study challenges the notion that glasses are simply kinetically arrested liquids. In addition, it shows that the non-equilibrium transition under pressure from LDA to HDA and from crystalline ice (Ih) to HDA is first-order like. The implications of these findings on the origin of the water anomalies will be discussed as well as their connection with the hydrogen bond network of water.