Computer simulations of the adsorption of xenon on stepped surfaces

Abstract

The results of grand canonical Monte Carlo simulations of the thermodynamic and structural properties of xenon adsorbed at 120K and 166 K on two stepped surfaces are presented. The solids consisted of graphite basal planes that were truncated to form steps that are two planes in height (i.e., 0.68 nm high) and perfectly straight; they differ in that the widths of the terraces were chosen to be 2.13nm and 4.26 nm. In addition, simulations were carried out for a reference solid that consisted of infinite flat basal planes. The results of the simulations for the stepped surfaces were broken down into two regions: (i) narrow strips at the bottoms of the steps that are characterized by strong holding potentials which cause the atoms in these regions to form approximately one-dimensional systems; and (ii) the remainder of the surfaces, which essentially is the terraces bounded on one side by the lines of atoms adsorbed at the bottoms of the steps and on the other by the much weaker holding potentials that are found at the tops of the steps. Although the finite size effects upon the properties of the two-dimensional fluid adsorbed on the strips that comprise the terraces are profound, this representation of these systems provides an adequate description of the simulation results, and points the way to a deeper analysis of the properties of gases on such surfaces.