GSI-FAIR Colloquium

Does water consist of two liquids? X-rays reveal water ́s mysteries

by Katrin Amann-Winkel (University of Stockholm)

Europe/Berlin
SB1 1.120 (GSI Main Lecture Hall)

SB1 1.120

GSI Main Lecture Hall

Description
Water is ubiquitous and the most important liquid for life on earth. Although the water molecule is seemingly simple, various macroscopic properties of water are most anomalous, such as the density maximum at 4°C or the divergence of the heat capacity upon cooling. The fundamental origin of these anomalies is yet to be fully understood [1]. Computer-simulations suggest that the anomalous behaviour of ambient and supercooled water could be explained by a two-state model of water. The amorphous forms of water play an important role in this ongoing debate [2]. Since the discovery of two distinct amorphous states of ice with different density (high- and low-density amorphous ice, HDA and LDA) it has been discussed whether and how this phenomenon of polyamorphism at high pressur es is connected to the occurrence of two distinct liquid phases (HDL and LDL) [3]. X-ray scattering experiments on both supercooled water and amorphous ice are of major importance for our understanding of water. In my talk I will give an overview on our recent experiments on supercooled water and amorphous ices. Femtosecond X-ray laser pulses are used to study the structure of liquid water in micrometer-sized water droplets at temperatures down to 227 K. X-ray correlation spectroscopy (XPCS) was used to study the dynamics in amorphous ice around the hypothesized glass transition temperature. Our results are consistent with the hypothesis of a liquid-liquid transition between HDL and LDL [4]. [1] Nilsson, A. & Pettersson, L.G.M., The structural origin of anomalous properties of liquid water. 6, 8998, Nature Comms (2015) [2] K. Amann-Winkel et al., Water ́s controversial glass transition, Rev. Mod. Phys. 88, 0110002 (2016) [3] P. Gallo, K. Amann-Winkel et al., Water: a Tale of Two Liquids, Chem. Rev. 116, 7463-7500 (2016) [4] F. Perakis, K. Amann-Winkel et al., Diffusive dynamics during the high-to-low density transition in amorphous ice, PNAS 114, 8193 (2017)
Poster