Structure in confined fluids: phase separation of binary simple liquid mixtures

One- to five-layer cyclohexane and octamethyltetracyclosiloxane (OMCTS) films confined between mica-like surfaces are studied to elucidate changes in the lattice type and composition of the films. Grand canonical ensemble Monte Carlo computer simulations are used to study the laterally confined film. In contrast to previous studies, solid-like order is induced primarily by the strong fluid-solid interaction and is largely a function of pore width. Solid-like order within the layers causes the composition of the pore fluid to shift from the bulk composition, favoring either cyclohexane or OMCTS, depending on the pore width. A shift in the relative alignment of the surfaces perturbs the solid-like fluid structure but does not cause the sudden shear melting transition associated with epitaxial alignment of the fluid atoms with the surface.