DOI: 10.1209/epl/i2003-00142-5
Europhys. Lett., 61 (5) , pp. 695-701 (2003)

Effect of many-body interactions on the solid-liquid phase behavior of charge-stabilized colloidal suspensions

J. Dobnikar¹, R. Rzehak² and H. H. von Grünberg<sup>1

1</sup>  Universität Konstanz, Fachbereich Physik - D-78457 Konstanz, Germany
²  Institut für Festkörperforschung, Forschungszentrum Jülich D-52425 Jülich, Germany

Jure.Dobnikar@uni-konstanz.de

(Received 9 September 2002; accepted in final form 17 December 2002)

Abstract
The solid-liquid phase diagram of charge-stabilized colloidal suspensions has been calculated using a technique that combines a continuous Poisson-Boltzmann description for the microscopic electrolyte ions with a molecular-dynamics simulation for the macroionic colloidal spheres. While correlations between the microions are neglected in this approach, many-body interactions between the colloids, mediated by the screening ionic fluid between them, are fully included. The Lindemann criterion has been used to determine the solid-to-liquid transition temperature in a colloidal system at a relatively high colloid volume fraction where many-body interactions are expected to be strong. With a view to the Derjaguin-Landau-Verwey-Overbeek theory predicting that colloids interact via Yukawa pair potentials, we compare our results with the phase diagram of a simple Yukawa liquid. We find an agreement under high-salt conditions, but considerable differences at low ionic strength. Using effective force calculations and data from molecular-dynamics simulations with simple model potentials, we further demonstrate that these differences are due to many-body interactions.

PACS
82.70.Dd - Colloids.
82.70.-y - Disperse systems; complex fluids.
05.20.Jj - Statistical mechanics of classical fluids.

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