Simulation of Surface Excess Concentrations for a Binary Hydrocarbon Mixture on Graphite

We perform Molecular Dynamics simulations of thin hydrocarbon films adsorbed on the basal plane of graphite to determine structural and thermodynamic properties. Specifically we study the behaviour of liquid benzene/n-heptane mixtures. The intra adsorbate and the adsorbate-substrate interactions are described using a phenomenological force field whose careful parameterization will be reported in a following paper. The foremost quantity we calculate is the adsorption isotherm, i.e. the surface excess concentration as a function of the benzene bulk mole fraction at T = 283 K, which is in quite reasonable agreement with the experiment. Along with the isotherm we compare the surface induced ordering of the two components in terms of order parameter profiles.