Based on a recently suggested density functional, a model for corrugational inert gas atom-metal surface potential energies for intermolecular interaction is obtained. The atom-atom potential energy summation is used, from where analytical fits are obtained for the potential energies for the gas-surface systems Ar-Cu(001), Kr-Cu(001) and Ar-Ag (001). Following the solution method for the Fokker-Planck equation due to Risken, coefficients for the tracer diffusion are obtained. Finally the results are discussed concerning the characteristics of the potential energy surfaces.