Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Confined Fluids

CPP 17.3: Talk

Tuesday, March 24, 2009, 10:00–10:15, ZEU 160

Phase transitions of charged colloidal suspensions in slit pores — •Stefan Grandner and Sabine H. L. Klapp — Institut für theoretische Physik, Freie Universität Berlin, D-14195 Berlin, Germany

Employing Monte Carlo simulations in grandcanonical and isobaric ensembles we investigate freezing phenomena in a charged colloidal suspension confined to narrow slit-pores [1]. The macroion interactions are described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential, which involves the counter- and salt ions implicitly, supplemented by a repulsive soft-sphere potential. Corresponding to experiments [2] we focus on moderately charged silica particles in solvents of low ionic strengths. The considered densities are too small to drive bulk freezing transitions. However, confining the suspension to sufficiently small pore widths does not only yield the well-known layering but also the formation of crystalline in-plane structures. This capillary freezing is consistent with ground-state calculations [3]. Furthermore, varying the parallel pressure at given surface separation we found a solid-solid transition from two-layer to three-layer systems with different in-plane order as found for uncharged spheres [4]. Finally, we consider the influence of wall charges including the possibility of charge-induced freezing.

[1] S. Grandner and S. H. L. Klapp, J. Chem. Phys., accepted.
[2] S. H. L. Klapp, D. Qu, and R. v. Klitzing, J. Phys. Chem. B 111, 1296 (2007); S. H. L. Klapp, Y. Zeng, D. Qu, and R. v. Klitzing, Phys. Rev. Lett. 100, 118303 (2008).
[3] R. Messina and H. Löwen, Phys. Rev. Lett. 91, 146101 (2003).
[4] A. Fortini and M. Dijkstra, J. Phys.: Cond. Matter 18, L371 (2006).