Monte Carlo studies on phase behavior and criticality of colloid-polymer mixtures in confined geometries

K. BINDER; J. HORBACH; R. L. C. VINK; A. DE VIRGILIIS

Sicilia (Italia)

Conferencia; SOCOBIM'07; 2007

SFB-TR6 (DFG,Alemania), INFM-CNR (Italia)

The Asakura-Oosawa (AO) model of colloid-polymer mixtures is studied by grand-canonicalMonte Carlo simulation in a L × L × D slit geometry, both at z = 0 and at z = D. Varyingthe lateral linear dimension L and applying finite size scaling analysis, the phase diagram andcritical behavior is obtained for a range of thin film thickness D. Both the cases of symmetricwalls and of competing walls are realized (in the latter case an additional repulsive wall po-tential on the colloids only is applied at the right wall). For symmetric walls, evidence for theNakanashi-Fisher scaling predictions for the shift of the critical point is obtained. For competingwalls, interface localization-delocalization transitions are observed. It is argued that a gradualcrossover from capillary condensation transitions to interface localization-delocalization transi-tions occurs when the strength of the repulsive wall potential is varied. The critical behavior ofall these transitions falls in the two-dimensional Ising universality class.