Thermodynamic properties of bulk and confined water

摘要

The thermodynamic response functions of water display anomalous behaviors. We study these anomalous behaviors in bulk and confined water. We use nuclear magnetic resonance (NMR) to examine the configurational specific heat and the transport parameters in both the thermal stable and the metastable supercooled phases. The data we obtain suggest that there is a behavior common to both phases: that the dynamics of water exhibit two singular temperatures belonging to the supercooled and the stable phase, respectively. One is the dynamic fragile-to-strong crossover temperature (T-L similar or equal to 225 K). The second, T* similar to 315 +/- 5 K, is a special locus of the isothermal compressibility K-T(T, P) and the thermal expansion coefficient alpha(P)(T, P) in the P-T plane. In the case of water confined inside a protein, we observe that these two temperatures mark, respectively, the onset of protein flexibility from its low temperature glass state (T-L) and the onset of the unfolding process (T*). (C) 2014 AIP Publishing LLC.