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Quantitative Assessment of the Accuracy of the Poisson–Boltzmann Cell Model for Salty Suspensions

Hallez, Yannick and Diatta, Joseph and Meireles, Martine Quantitative Assessment of the Accuracy of the Poisson–Boltzmann Cell Model for Salty Suspensions. (2014) Langmuir, vol. 30 (n° 23). pp. 6721-6729. ISSN 0743-7463

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Official URL: http://dx.doi.org/10.1021/la501265k

Abstract

The cell model is a ubiquitous, fast, and relatively easily implemented model used to estimate the osmotic pressure of a colloidal dispersion. It has been shown to yield accurate approximations of the pressure in dispersions with a low salt content. It is generally accepted that it performs well when long-ranged interactions are involved and the structure of the dispersion is solidlike. The aim of the present work is to determine quantitatively the error committed by assuming the pressure computed with the cell model is the real osmotic pressure of a dispersion. To this end, cell model pressures are compared to a correct estimation of the actual pressures obtained from Poisson–Boltzmann Brownian dynamics simulations including many-body electrostatics and the thermal motion of the colloids. The comparison is performed for various colloidal sizes and charges, salt contents, and volume fractions. It is demonstrated that the accuracy of the cell model predictions is a function of only the average intercolloid distance scaled by Debye’s length κd̅ and the normalized colloidal charge. The cell model is accurate for κd̅ < 1 and not reliable for κd̅ > 5 independently of the colloidal charge. In the 1 < κd̅ < 5 range, covering a wide set of experimental conditions, the colloidal surface charge has a large influence on the error associated with the cell approximation. The results presented in this article should provide a useful reference to determine a priori if the cell model can be expected to predict accurately an equation of state for a given set of physicochemical parameters.

Item Type:Article
Additional Information:Thanks to the American Chemical Society. The definitive version is available at http://pubs.acs.org The original PDF of the article can be found at Langmuir website : http://pubs.acs.org/doi/abs/10.1021/la501265k
HAL Id:hal-01250376
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS (FRANCE)
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Deposited By: Yannick HALLEZ
Deposited On:07 Jul 2014 14:55

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