Critical phenomena in colloid-polymer mixtures: interfacial tension, order parameter, susceptibility, and coexistence...

The critical behavior of a model colloid-polymer mixture, the so-called Asakura-Oosawa (AO) model, is studied using computer simulations and finite size scaling techniques. Investigated are the interfacial tension, the order parameter, the susceptibility, and the coexistence diameter. Our results clearly show that the interfacial tension vanishes at the critical point with exponent 2nu approximately 1.26 . This is in good agreement with the 3D Ising exponent. Also calculated are critical amplitude ratios, which are shown to be compatible with the corresponding 3D Ising values. We additionally identify a number of subtleties that are encountered when finite size scaling is applied to the AO model. In particular, we find that close to the critical point, the finite size extrapolation of the interfacial tension is most consistent when logarithmic size dependences are ignored.