The Water Polymorphism and the Liquid–Liquid Transition from Transport Data

Francesco Mallamace,Georgia Papanikolaou,Giuseppe Mensitieri,Sow-Hsin Chen,Paola Lanzafame,Domenico Mallamace

doi:10.3390/physchem1020014

Abstract

NMR spectroscopic literature data are used, in a wide temperature-pressure range (180–350 K and 0.1–400 MPa), to study the water polymorphism and the validity of the liquid–liquid transition (LLT) hypothesis. We have considered the self-diffusion coefficient DS and the reorientational correlation time τθ (obtained from spin-lattice T1 relaxation times), measured, respectively, in bulk and emulsion liquid water from the stable to well inside the metastable supercooled region. As an effect of the hydrogen bond (HB) networking, the isobars of both these transport functions evolve with T by changing by several orders of magnitude, whereas their pressure dependence become more and more pronounced at lower temperatures. Both these transport functions were then studied according to the Adam–Gibbs model, typical of glass forming liquids, obtaining the water configurational entropy and the corresponding specific heat contribution. The comparison of the evaluated CP,conf isobars with the experimentally measured water specific heat reveals the full consistency of this analysis. In particular, the observed CP,conf maxima and its diverging behaviors clearly reveals the presence of the LLT and with a reasonable approximation the liquid–liquid critical point (LLCP) locus in the phase diagram.

Highlights

Water, starting from the perspective of biology, has a basic role in many research fields and technological applications, regardless of whether it is in bulk or confined [1]
In the figure inset, ∆CP is reported as the difference between the specific heat values measured in the liquid and in the ice Ih, respectively, and the CP,con f evaluated by using the Adam–Gibbs model (AG) theory as described in the following [47]
Starting from the idea that liquid water is dominated by a polymorphism generated by the hydrogen bond (HB) interactions and that this polymorphism, made from the LDL and HDL, dominates the behavior of thermodynamical functions, we have analyzed a lot of experimental data that enter well inside the no man’s land in order to determine what they can tell us about the presence of the liquid–liquid transition (LLT) and more generally what they reveal about the liquid–liquid critical point (LLCP) hypothesis

Summary

Introduction

Water, starting from the perspective of biology, has a basic role in many research fields and technological applications, regardless of whether it is in bulk or confined [1].

Results

Conclusion