Regensburg 2016 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Statistical Physics (general)

DY 13.8: Vortrag

Montag, 7. März 2016, 16:45–17:00, H48

Analytical one-dimensional approach of understanding water anomalies and phase transitions — •Katharina Ferling and Andreas Heuer — Institut für Physikalische Chemie, WWU Münster, Germany

The understanding of the water behaviour, including its anomalies, can play an important role in improving the description of water. Here the emphasis lies on the property of building H-bonds which is believed to be one major factor for many anomalies such as the density change or the liquid-liquid phase transition at low temperatures. For the present investigation a simple model has been chosen which focuses on the distinction between a close-packed and an open structure. The one dimensional model - which was first introduced by Ben-Naim [1] - has now been extended by terms, capturing the interaction of second-nearest neighbours as well as the transition to the gas phase at high temperatures. Here, two different analytical approaches are evaluated via explicit calculation of the partition function, and selected properties are discussed with the aim to show water-like behaviour such as a high-density liquid and low-density liquid (HDL-LDL) transition. One model shows a clear first order phase transition between a high-density and a low-density phase and both models have a (theoretical) transition line with negative slope in the p-T plane. Furthermore, anomalous behaviour of several properties, such as the density, heat capacity and isothermal compressibility, is visible, as can be seen in real water.

[1] Arieh Ben-Naim, J. Chem. Phys. 128, 024505 (2008)