STRUCTURAL STUDIES OF HIGHLY CORRUGATED SURFACES WITH ATOMIC-BEAMS - CALCULATION OF HE-DIFFRACTION INTENSITIES FROM REALISTIC INTERACTION POTENTIALS WITH AN EXTENDED GR-METHOD

An extended GR-method for the calculation of He-diffraction intensitie s from highly corrugated surfaces in connection with realistic He/surf ace interaction potentials making use of a "step approximation" is pre sented. Numerical results are in excellent agreement with close couple d channels calculations (CCC) and reproduce experimental He-diffractio n data from the missing-row reconstructed Pt(110)(1 x 2). The method i s more transparent than CCC, since beams can be traced during their pa ssage through the interaction potential: It thus reveals why neglect o f attractive potential corrugation leads to an overestimation of surfa ce corrugation amplitudes. The method can also be applied to resonant scattering and leads to an explanation why for highly corrugated syste ms purely elastic calculations reproduce experimental resonant structu res in contrast to systems with small corrugations.