Monte Carlo simulations of phase transitions of systems in nanoscopic confinement

When simple or complex fluids are confined to ultrathin films or channels or other cavities of nanoscopic linear dimensions, the interplay of finite size and surface controls the phase behavior, and may lead to phase transitions rather different from the corresponding phenomena in the bulk. Monte Carlo simulation is a very suitable tool to clarify the complex behavior of such systems, since the boundary conditions providing the confinement can be controlled and arbitrarily varied, and detailed structural information on the inhomogeneous states of the considered systems is available. Examples used to illustrate these concepts include simple Ising models in pores and double-pyramid-shaped cavities with competing surface fields, where novel types of interface localization-delocalization phenomena occur accompanied by “macroscopic” fluctuations, and colloid-polymer mixtures confined in slit pores. Finite size scaling concepts are shown to be a useful tool also for such systems “in between” the dimensionalities.