A computer simulation and experimental study of the difference between krypton adsorption on a graphite surface and in a graphitic hexagonal pore

Adsorption isotherms and isosteric heats have been studied experimentally and by computer simulation for the krypton-graphitic hexagonal pore and krypton–graphite planar surface systems in the 60–109 K temperature range. The existence of a 2D transition in the sub-monolayer film on the basal plane of graphite that is observed experimentally is confirmed by the computer simulation results, but this transition is not observed in graphitic hexagonal pores because the onset of adsorption occurs at the junctions of adjacent pore walls, and the mechanism of surface adsorption is the spreading of adsorbate from the junction towards the basal planes until the first layer is completed. This is followed by molecular layering of higher layers, and then by capillary condensation when the empty core is small enough.