Competing coexisting phases in 2D water.

Jean-Marc Zanotti,Marco Bonetti,Jean-Blaise Brubach,Marie-Claire Bellissent-Funel,Dimitrios Sakellariou,Jacques Ollivier,Simona Dalla-Bernardina,Pascale Roy,Patrick Judeinstein,Gaëlle Creff

doi:10.1038/srep25938

Abstract

The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules.

Highlights

In bulk water, local energetics and long-range connectivity come along with a very specific local three-dimensional (3D) tetrahedral organization of the hydrogen bond (HBond) network (Fig. 1a)
Vycor, with its perfect non fluctuation and homogeneous surface and structure, can be considered as a pure model system for physicist, we think that the temperature transitions of 2D water we report in this paper have a general relevance
We account for the transient and fluctuating HBond network of 2D water by a simple and purely analytical mean-field percolation model

Summary

Introduction

Local energetics and long-range connectivity come along with a very specific local three-dimensional (3D) tetrahedral organization of the hydrogen bond (HBond) network (Fig. 1a). Transport of water molecules in Carbon NanoTubes (CNT), can be cited as an emblematic example[3] of how the frustration of the natural 3D tetrahedral organization of the hydrogen bond network by confinement profoundly modifies the water physical properties: when trapped inside CNT, water is found to flow-up three orders of magnitude faster than predicted by the continuum hydrodynamics picture. This is the consequence of the peculiar organization of the water hydrogen bond network imposed by the restricted radial volume of the tube. Molecular Dynamics (MD) simulations data have shown that, even when the surface locally imposes a crystal orientational order, the formation of unfreezable surface water is controlled by the cylindrical pore curvature that induces spontaneous positional disorder preventing the formation of a long range crystalline HBond network

Results

Discussion

Conclusion