Atom scattering from surfaces with isolated impurities: Calculations for hard wall and soft potentials
The angular intensity distribution for atom scattering from surfaces with isolated defects is calculated. For a two-dimensional model time-dependent wave packet calculations are carried out for potentials with different steepness and variable defect size and height. The influence of the potential softness is studied by comparison with results from a corresponding hard wall model. Within the hard wall model the Eikonal approximation (EA) and an improved Eikonal approximation (IEA) which accounts for double collision effects are tested against numerically exact results. While, in general, the EA works well only in the vicinity of the specular peak the IEA is quite accurate over the entire angular range. Finally, wave packet calculations are carried out for a model of a flat surface with isolated steps, fitted to represent a stepped Pt(111) surface. The results are compared to recent measurements of the incoherent elastic diffraction for this system. Basic measured features like a rainbow maximum and large angle interference oscillations are well reproduced by the calculations.