By means of a density functional approach, the phase equilibria of a fluid confined between two adsorbing walls, i.e., in a slitlike capillary, have been investigated. The theory provides a microscopic basis for the phenomenon of capillary condensation and, for fluids in narrow slits, predicts a line of critical points marking the end of the lines of coexistence between "liquid" and "gas" phases.

• Received 3 October 1983

DOI:https://doi.org/10.1103/PhysRevLett.52.557