Damping functions for the pairwise sum model of the atom-surface potential

A pairwise sum model is used to derive the laterally averaged atom-surface potential using the Tang-Toennies potential for interactions between a free atom and the atoms in a solid. The atom-surface van der Waals attraction is shown to include all multipole terms with the proper damping. The analytical expressions for the damping functions have the same damping parameter as for the free atom-atom interactions. (C) 2002 American Institute of Physics.