Regensburg 2004 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 17: Fluids II
DY 17.5: Vortrag
Montag, 8. März 2004, 17:30–17:45, H3
Adsorption of an asymmetric binary mixture at a selective solid wall — •Dirk Woywod, Jörg Silbermann, and Martin Schoen — Stranski-Laboratorium für Physikalische und Theoretische Chemie
TU Berlin
Sekretariat TC 7
Strasse des 17.Juni 124
10623 Berlin
We consider a binary (A-B) mixture fluid near a selective planar
homogenous wall. Using a lattice-gas model and mean-field
approximation to the intrinsic free-energy functional, we obtain a
closed expression for the potential density in the grand canonical
ensemble (V,T,µA=µB). This expression depends on the
attraction strength of the fluid-fluid interactions
(єAA>єBB, єAB), the fluid-wall
interactions (єAW<єBW), and the local densities
(ρA, ρB). Minimizing the potential density numerically
gives us access to complete phase diagrams including
wetting films [1].
In this presentation, we choose bulk parameters in order to promote
the formation of demixed A-rich liquid phases near coexistence with a
gas phase. Introducing a preference of the wall for molecules of
component B, first-order phase transitions between adsorbed mixed,
A-rich and B-rich films are observed. Besides multiple surface
critical points, we also find a peculiar temperature dependence of the
concentration of component B
within a B-rich mixed film.[2]
[1] D. Woywod, M. Schoen, Phys. Rev. E 67, 026122 (2003)
[2] J. Silbermann, D. Woywod, M. Schoen, Phys. Rev E, in press (2003)