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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 13: Glasses (original: DY, joined by DF, CPP)

CPP 13.1: Vortrag

Montag, 31. März 2014, 15:00–15:15, ZEU 146

Dynamic Crossover and Stepwise Solidification of Confined Water — •Matthias Sattig and Michael Vogel — Hochschulstraße 6, D-64289 Darmstadt

The dynamical behaviour of water in the regime of the supercooled liquid is still a topic of large interest. In particular, the existence of a fragile-to-strong transition (FST) at around 225K induced by a liquid-liquid phase transition (LL) is controversially discussed [1]. The proposed temperature range of the FST is hardly accessible in bulk water.

Our ²H NMR investigation reveals two dynamic crossovers of supercooled water in nanoscopic (nm) confinement. A dynamic crossover of liquid water at ca. 225K is accompanied by a formation of a fraction of solid water. Therefore, this effect can not be attributed to the LL, but rather to a change from liquid-like to interface-dominated dynamics. Moreover, the ²H NMR data yield evidence that the α process and β process are observed in experiments above and below this temperature, respectively. Upon cooling through a dynamic crossover at ca. 175K, the dynamics of the liquid fraction becomes anisotropic and localized, implying solidification of the corresponding water network, most probably, during a confinement-affected glass transition.

[1] Mishima; Nature, Vol. 396, 329(1998)