Shear-induced phase transitions in confined lattice gases

Abstract

The phase behaviour of a fluid confined between two plane-parallel solid substrates is investigated within the framework of lattice-gas calculations where the mean-field intrinsic free energy is employed. By minimizing the grand potential numerically, phase diagrams are constructed. Substrates are composed of alternating strips of weakly and strongly adsorbing material. The lattice gas may consist of a high-density region stabilized by the strongly adsorbing portion of the substrate while a low-density region exists over the weakly adsorbing ones (the `bridge' phase). The `bridge' phases coexist with either a liquidlike or a gaslike phase occupying the entire space between the substrates. All three phases join at a triple point, and two critical points exist at which the `bridge' and gaslike phases or `bridge' and liquidlike phases become (separately) indistinguishable. By misaligning the substrates in the x-direction, the lattice gas can be exposed to a shear strain which causes the width of the one-phase region for the `bridge' phases to vary and the triple-point location to alter.