Hydration of Cl– ion in a planar nanopore with hydrophilic walls. 2. Thermodynamic stability

Abstract

The Monte Carlo bicanonical statistical ensemble method has been employed to calculate the dependences of the Gibbs free energy, formation work, and entropy on the size of a hydration shell grown from water vapor on single-charged chlorine anion in a model planar nanopore with hydrophilic structureless walls at 298 K. A refined model comprising many-particle polarization interactions and calibrated with respect to experimental data on the free energy and enthalpy of the initial reactions of attachment of water molecules to the ion has been used. It has been found that a weak hydrophilicity of pore walls leads to destabilization of the hydration shell, while a strong one, on the contrary, causes its stabilization. The physical reason for the instability in the field of hydrophilic walls qualitatively differs from that under the conditions of hydration in bulk water vapor.