The amount of energy needed to bring N2 molecule from the equilibrium distance to 0.20 nm from a given adsorption site was estimated by taking energy difference between the equilibrium geometry and a fixed geometry where N2 was rigidly translated closer to the surface. Since no further relaxation was considered for these last geometries in the highly repulsive part of the potential, the calculated energies should be used with caution and should be considered as upper limits. More rigorous calculations are necessary to accurately evaluate those energies in order to be compared directly to experimental values.