We have extended the electron gas model due to Gordon and Kim to calculate the interaction energies of multi-atom and multi-adatom-molecule systems. We present our extension and the preliminary results of the effect of the basis sets used to describe the components on the predicted equilibrium geometries. Finally we compare the results calculated using this model to results using a 6–12 type potential for the predicted equilibrium geometries of benzene-argon and anthracene-argon complexes for one and two bound adatoms.