Research news

State of water in the model: (a) steam hydrogen bond, (b) steam contact without hydrogen bond, (c) without interaction, (d) cage-like structure.
Image source: Tomaž Urbič

Publish Date: 19.12.2019

Category: Outstanding research achievements, Interdisciplinary research

The statistical and mechanical model of water developed by researchers from the Faculty of Chemistry and Chemical Technology of the University of Ljubljana and Stony Brook University, New York, points to its cage-like form and predicts well its energetic and volumetric properties.

 Authors: Tomaž Urbič, Ken A. Dill

The properties of liquid water have still not yet been fully understood. We are still not able to explain well how the properties of water are encoded in its molecular structure. The researchers, from the Faculty of Chemistry and Chemical Technology of the University of Ljubljana (Tomaž Urbič) and the State University of New York at Stony Brook (Ken A. Dill), developed a statistical and mechanical model of water called CageWater, with which they described the interaction between molecules of water with hydrogen bonds and Van der Waals contact.

The model predicts well the energetic and volumetric properties of water and its anomalous properties, such as maximum density in the liquid range, high heat capacity and so on. It has been developed in such a way that it does not require much time to calculate the properties of water. In comparison with computer simulations, the calculations are made in an instant. The development of this model has served to improve our understanding of water.

For a long time we have anticipated that water is a liquid of two densities, a relatively dense Lennard-Jones liquid and a less dense liquid dominated by hydrogen bonds. In their model the researchers found that the hydrogen bonds affects density, and the involvement of hydrogen bonds in the cage-like structures causes the open structure of water. This balance changes with temperature and density. The model can also be used to explain the structural changes in the liquid-liquid transition in subcooled water.

Source: Urbič T., Dill K. A. Water is a cagey liquid. J. Am. Chem. Soc., 140 (2019), 17106-17113. 

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