Molecular Dynamics Study of Krypton Isotopes Physisorbed on Graphite
Desorption of adsorbed Krypton isotopes is studied via Molecular Dynamics as a function of temperature, density and adsorbed layers. The model simulates a 50-50 mixture of Krypton isotopes where the multilayer systems are built around the first layer which is commensurate with the graphite substrate. It is shown that desorption of an isotropic mixture in a multilayered system (layers > 2) exhibits a separation that is equivalent to Graham's Law while a monolayer system exhibits a separation of the isotopes that is significantly higher. The enhanced effect seen in the monolayer studies is believed to be due to the confinement provided by the graphite substrate. The validation was performed by calculating the vapor pressure of the system as well identifying the melting point of a commensurate monolayer of Kr physisorbed onto graphite. The results of the validation agree within 6% of the experimental results. The limitations of the model as well as possible consequences are presented as well.