Condensed Matter Physics, 2017, vol. 20, No. 3, 33005
DOI:10.5488/CMP.20.33005

Title: Solvation in atomic liquids: connection between Gaussian field theory and density functional theory
Author(s):
  V. Sergiievskyi (Sorbonne Universités, UPMC Univ Paris 06, ENS, CNRS, UMR 8640 PASTEUR, 75005 Paris, France) ,
  M. Levesque (Sorbonne Universités, UPMC Univ Paris 06, ENS, CNRS, UMR 8640 PASTEUR, 75005 Paris, France) ,
  B. Rotenberg (Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8234 PHENIX, 4 Place Jussieu, 75005 Paris, France) ,
  D. Borgis (Sorbonne Universités, UPMC Univ Paris 06, ENS, CNRS, UMR 8640 PASTEUR, 75005 Paris, France; Maison de la Simulation, CEA, CNRS, Univ. Paris-Sud, UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France)

For the problem of molecular solvation, formulated as a liquid submitted to the external potential field created by a molecular solute of arbitrary shape dissolved in that solvent, we draw a connection between the Gaussian field theory derived by David Chandler [Phys. Rev. E, 1993, 48, 2898] and classical density functional theory. We show that Chandler's results concerning the solvation of a hard core of arbitrary shape can be recovered by either minimising a linearised HNC functional using an auxiliary Lagrange multiplier field to impose a vanishing density inside the core, or by minimising this functional directly outside the core — indeed a simpler procedure. Those equivalent approaches are compared to two other variants of DFT, either in the HNC, or partially linearised HNC approximation, for the solvation of a Lennard-Jones solute of increasing size in a Lennard-Jones solvent. Compared to Monte-Carlo simulations, all those theories give acceptable results for the inhomogeneous solvent structure, but are completely out-of-range for the solvation free-energies. This can be fixed in DFT by adding a hard-sphere bridge correction to the HNC functional.

Key words: statistical mechanics, classical fluids, 3-dimensional systems, density functional theory, gaussian field theory
PACS: 05.20.Jj, 11.10.-z, 82.60.Lf, 64.75.Bc


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