  Surface Patterson Functions have been derived by direct inversion of
experimental Low-Energy Electron Diffraction I-V spectra measured at multiple
incident angles. The direct inversion is computationally simple and can be used
to discriminate between different structural models. 1x1 YSi_2 epitaxial layers
grown on Si(111) have been used to illustrate the analysis. We introduce a
suitable R-factor for the Patterson Function to make the structural
discrimination as objective as possible. From six competing models needed to
complete the geometrical search, four could easily be discarded, achieving a
very significant and useful reduction in the parameter space to be explored by
standard dynamical LEED methods. The amount and quality of data needed for this
analysis is discussed.
