A simple analysis of ion–ion correlation in polyelectrolyte solutions

• DOI: 10.1063/1.458022
• Publication Date: 2002-07-26T13:12:26Z
• Authors: Robert Penfold; Sture Nordholm; Bo Jönsson; C. E. Woodward
• Keywords: 0103 physical sciences; 02 engineering and technology; 0210 nano-technology; 01 natural sciences

In the Poisson–Boltzmann theory of macroion screening in electrolyte solutions the chief simplifying assumption is the neglect of correlations within the ionic atmosphere. Using a generalized van der Waals density functional analysis incorporating ion–ion correlation in a local approximation we obtain a simple correlation corrected Poisson–Boltzmann theory. For point charges in the salt free case, this local correlation approximation leads to asymptotic instability (a ‘‘structuring catastrophe’’) though the correction is well behaved to low orders in perturbation theory. Results in zeroth order and in a zeroth order field approximation are compared with an extended series of Monte Carlo simulations within a cell model (and a planar electrode model). An excellent agreement is found over a wide range of coupling strengths.