SITE-DEPENDENT ENERGY-LOSS IN AR SCATTERING FROM PT(111)

Using classical trajectory calculations the translational energy ratio of the final and initial energy (E(f)/E(i)) for Ar inelastically scattered from a Pt(111) surface has been investigated for thermal and-hyperthermal energies up to 30 eV. The Ar/Pt(111) potential is based on a Hartree-Fock-Slater calculation for an Ar atom with a Pt4-cluster. The energy ratio varies strongly across the surface unit cell. There is a most unusual energy dependence: for energies below 16 eV the atop site shows the larger loss than the bridge and centre sites, whereas for higher energies the situation is reversed. This reversal can be understood in terms of a simple analytical model. The calculations show a site dependent onset for trapping and implantation.