COMPUTER-SIMULATIONS OF THE ADSORPTION OF XENON ON STEPPED SURFACES

The results of grand canonical Monte Carlo simulations of the thermody namic and structural properties of xenon adsorbed at 120K and 166K on two stepped surfaces are presented. The solids consisted of graphite b asal planes that were truncated to form steps that are two planes in h eight (i.e., 0.68 nm high) and perfectly straight; they differ in that the widths of the terraces were chosen to be 2.13 nm and 4.26 nm. In addition, simulations were carried out for a reference solid that cons isted of infinite flat basal planes. The results of the simulations fo r the stepped surfaces were broken down into two regions: (i) narrow s trips at the bottoms of the steps that are characterized by strong hol ding potentials which cause the atoms in these regions to form approxi mately one-dimensional systems; and (ii) the remainder of the surfaces , which essentially is the terraces bounded on one side by the lines o f atoms adsorbed at the bottoms of the steps and on the other by the m uch weaker holding potentials that are found at the tops of the steps. Although the finite size effects upon the properties of the two-dimen sional fluid adsorbed on the strips that comprise the terraces are pro found, this representation of these systems provides an adequate descr iption of the simulation results, and points the way to a deeper analy sis of the properties of gases on such surfaces.