Understanding depletion induced like-charge attraction from self-consistent field model

Pei Liu; Manman Ma; Zhenli Xu

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arXiv · 1507.04815

Understanding depletion induced like-charge attraction from self-consistent field model

Pei Liu·Manman Ma·Zhenli Xu

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Abstract

The interaction force between likely charged particles/surfaces is usually repulsive due to the Coulomb interaction. However, the counterintuitive like-charge attraction in electrolytes has been frequently observed in experiments, which has been theoretically debated for a long time. It is widely known that the mean field Poisson-Boltzmann theory cannot explain or predict this anomalous feature since it ignores many-body properties. In this paper, we develop efficient algorithm and perform the force calculation between two interfaces using a set of self-consistent equations which properly takes into account the electrostatic correlation and the dielectric-boundary effects. By solving the equations and calculating the pressure with the Debye-charging process, we show that the self-consistent equations could be used to study the attraction between like-charge surfaces from weak-coupling to mediate-coupling regime, and that the attraction is due to the electrostatics-driven entropic force which is significantly enhanced by the dielectric depletion of mobile ions. A systematic investigation shows that the interaction forces can be tuned by material permittivity, ionic size and valence, and salt concentration, and that the like-charge attraction exists only for specific regime of these parameters.

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Pei Liu, Manman Ma, Zhenli Xu. 2015-07-17. Understanding depletion induced like-charge attraction from self-consistent field model. https://arxiv.org/abs/1507.04815

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