Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 2: Colloide, Nanopartikel und Kapseln

CPP 2.9: Vortrag

Montag, 24. März 2003, 12:15–12:30, ZEU/260

Colloidal particle at a liquid-vapor interface — •Martin Oettel und Siegfried Dietrich — Max-Planck-Institut f. Metallforschung, Heisenbergstr.3, 70569 Stuttgart

Quite recently the trapping of colloidal particles at various types of interfaces has been demonstrated experimentally and used for the assembly of regular colloidal structures, see e.g. ref. [1]. Here we investigate the effective potential of a larger colloidal particle in the proximity of the liquid-vapor interface of a fluid composed of smaller particles. The effective potential is equivalent to the change in chemical potential if the colloidal particle is inserted into the fluid. Using Widom’s insertion method (also referred to as the potential distribution theorem) this change in chemical potential is completely determined by the knowledge of the direct correlation functions for a homogeneous mixture of colloids and fluids in the limit of vanishing colloid density [2]. For hard colloids, these are calculated by a RHNC-type equation with a bridge function derived from Rosenfeld’s hard-sphere density functional [3]. Using these solutions, an effective density functional for the colloid-fluids mixture can be constructed. This can be used to assess the consistency of the insertion method.
[1] M.G. Nikolaides, A.R. Bausch, M.F.Hsu, A.D. Dinsmore, M.P.Brenner, C. Gay, and D.A. Weitz, Nature 420 (2002), 299.
[2] R. Roth, R. Evans, and S. Dietrich, Phys. Rev. E62 (2000), 5360.
[3] Y. Rosenfeld, J. Chem. Phys. 98 (1993), 8126.