Incorporation of excluded-volume correlations into Poisson-Boltzmann theory

Dmytro Antypov, Marcia C. Barbosa, and Christian Holm
Phys. Rev. E 71, 061106 – Published 22 June 2005

Abstract

We investigate the effect of excluded-volume interactions on the electrolyte distribution around a charged macroion. First, we introduce a criterion for determining when hard-core effects should be taken into account beyond standard mean-field Poisson-Boltzmann (PB) theory. Next, we demonstrate that several commonly proposed local-density-functional approaches for excluded-volume interactions cannot be used for this purpose. Instead, we employ a nonlocal excess free energy by using a simple constant-weight approach. We compare the ion distribution and osmotic pressure predicted by this theory with Monte Carlo simulations. They agree very well for weakly developed correlations and give the correct layering effect for stronger ones. In all investigated cases our simple weighted-density theory yields more realistic results than the standard PB approach, whereas all local density theories do not improve on the PB density profiles, but on the contrary, deviate even more from the simulation results.

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  • Received 15 February 2005

DOI:https://doi.org/10.1103/PhysRevE.71.061106

©2005 American Physical Society

Authors & Affiliations

Dmytro Antypov1,*, Marcia C. Barbosa2,†, and Christian Holm3,1,‡

  • 1Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
  • 2Instituto de Física, UFRGS, 91501-970, Porto Alegre, RS, Brazil
  • 3Frankfurt Institute for Advanced Studies (FIAS), Johann Wolfgang Goethe Universität, Max-von-Laue-Strße 1, D-60438 Frankfurt am Main, Germany

  • *Electronic address: antypov@mpip-mainz.mpg.de
  • Electronic address: barbosa@if.ufrgs.br
  • Electronic address: c.holm@fias.uni-frankfurt.de

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Issue

Vol. 71, Iss. 6 — June 2005

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