Computer Simulation Study of the Multilayer Adsorption of Fluid N2 on Graphite

Computer simulations of nitrogen adsorbed on the graphite basal plane at 73.6 K are reported for coverages ranging from ~1 monolayer to ~2.5 layers. Quantities evaluated include average potential energies and the component molecule-solid and molecule-molecule parts of these energies, translational and orientational order parameters of N2 molecules at the surface, and molecular pair correlation functions projected onto planes parallel to the surface. It is shown that both the orientations and the density of molecules in the first layer change as the total coverage changes, that there is a definite preference for the commensurate (or (√3×√3)R30°) translational ordered structure for first-layer molecules, and that the presence of a dense second layer can actually cause a slight decrease in the number of molecules held in the first layer. Comparisons with available experimental data are good, indicating that the simulations are based on a realistic model of the actual N2-graphite system. © 1986, American Chemical Society. All rights reserved