Molecular Distributions in a “Vapor–Liquid” Separating System Inside Cylindrical Pores at Three-Phase Boundaries

Abstract—

Three types of two-phase interfaces: vapor–liquid, solid–vapor, and solid–liquid, in a “vapor–liquid meniscus”—inside long isolated and limited connected cylindrical pores was described in terms of the lattice-gas model. This approach provides the uniformly precise calculations of the molecular distributions in inhomogeneous transition regions of all interfaces. The pore walls are considered nondeformable, and they form an external field for separating liquid. Adsorption films are formed on the pore surface due to the adsorbate–adsorbent interaction potential. The change in the potential of a flat wall due to the curvature of the pore surface is considered. The state of the “vapor in a pore” and “liquid in a pore” coexisting phases satisfy the equality of chemical potentials, excluding the appearance of metastable states. The conjunction regions between pores of different diameters and their influence on the meniscus formation are considered. The conditions for identifying the regions of the system that are outside the solid–liquid–vapor three-phase contact are discussed. A procedure for introducing a contact angle in the liquid–vapor–solid pore-wall system via molecular distributions of the adsorbate in a slitlike pore is described. The dependences of the width of the considered interfaces and contact angles are plotted as a function of the pore width and potential of pore walls.