Abstract

We show that single-file water in nanopores can be viewed as a one-dimensional (1D) Ising model, and we investigate, on the basis of this, the static dielectric response of a chain of hydrogen-bonded water molecules to an external field. To achieve this, we use a recently developed dipole lattice model that accurately captures the free energetics of nanopore water. In this model, the total energy of the system can be expressed as the sum of the effective interactions of chain ends and orientational defects. Neglecting these interactions, we essentially obtain the 1D Ising model, which allows us to derive analytical expressions for the free energy as a function of the total dipole moment and for the dielectric susceptibility. Our expressions, which agree very well with simulation results, provide the basis for the interpretation of future dielectric spectroscopy experiments on water-filled nanopore membranes.

Highlights

  • Water confined to hydrophobic, sub-nanometre channels forms single-file chains in which each water molecule is hydrogen-bonded to its nearest neighbours [1]

  • We show that single-file water in nanopores can be viewed as a one-dimensional Ising model and investigate, on this basis, the static dielectric response of a chain of hydrogen-bonded water molecules to an external field

  • We use a recently developed dipole lattice model which accurately captures the free energetics of nanopore water

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Summary

Introduction

Sub-nanometre channels forms single-file chains in which each water molecule is hydrogen-bonded to its nearest neighbours [1]. A convenient formulation of the model, the charge picture, in which the energy is expressed as sum of Coulomb-like interactions between defects and chain ends, permits to carry out computer simulations of water-filled narrow pores from nanoscopic to macroscopic lengths and spanning multiple time scales [14]. Using this model, we have recently shown how these unique ordering properties of nanoconfined water can be probed experimentally by dielectric spectroscopy and how the excitation energy, the diffusion.

From the dipole model to the Ising model
Dipole lattice model
Charge picture
Ising model
Uncorrelated defects and defect pairs
Total dipole moment distribution
Static dielectric response
Conclusion
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