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# Interfacial and wetting properties of a binary point Yukawa fluid

journal contribution

posted on 2014-10-08, 13:20 authored by Paul Hopkins, Andrew ArcherAndrew Archer, Robert EvansWe investigate the interfacial phase behavior of a binary fluid mixture composed of repulsive point Yukawa particles. Using a simple approximation for the Helmholtz free energy functional, which yields the random phase approximation for the pair direct correlation functions, we calculate the equilibrium fluid density profiles of the two species of particles adsorbed at a planar wall. We show that for a particular choice (repulsive exponential) of the wall potentials and the fluid pair-potential parameters, the Euler–Lagrange equations for the equilibrium fluid density profiles may be transformed into a single ordinary differential equation and the profiles obtained by a simple quadrature. For certain other choices of the fluid pair-potential parameters fluid-fluidphase separation of the bulk fluid is observed. We find that when such a mixture is exposed to a planar hard wall, the fluid exhibits complete wetting on the species 2 poor side of the binodal, i.e., we observe a thick film of fluid rich in species 2 adsorbed at the hard wall. The thickness of the wettingfilm grows logarithmically with the concentration difference between the fluid state point and the binodal and is proportional to the bulk correlation length of the intruding (wetting) fluid phase. However, for state points on the binodal that are further from the critical point, we find there is no thick wettingfilm. We determine the accompanying line of first-order (prewetting) surface phase transitions which separate a thin and thick adsorbed film. We show that for some other choices of repulsive wall potentials the prewetting line is still present, but its location and extent in the phase diagram is strongly dependent on the wall-fluid interaction parameters.

## Funding

### P.H. thanks EPSRC and A.J.A. thanks RCUK for financial support.

## History

## School

- Science

## Department

- Mathematical Sciences

## Published in

JOURNAL OF CHEMICAL PHYSICS## Volume

129## Issue

21## Pages

? - ? (10)## Citation

HOPKINS, P., ARCHER, A.J. and EVANS, R., 2008. Interfacial and wetting properties of a binary point Yukawa fluid. Journal of Chemical Physics, 129 (21), 214709.## Publisher

© American Institute of Physics## Version

- VoR (Version of Record)

## Publication date

2008## Notes

Copyright 2008 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Chemical Physics, 2008, 129 (21), 214709 and may be found at: http://dx.doi.org/10.1063/1.3027515## ISSN

0021-9606## Publisher version

## Language

- en