STRUCTURE DETERMINATION OF PT3TI(111) BY AUTOMATED TENSOR LEED

An analysis of low-energy electron diffraction (LEED) I-V spectra from the clean Pt3Ti(111) surface was performed by comparing measured intensities with data calculated using an automated tensor LEED program, which employs a directed search optimization procedure. It was found that the topmost layer is pure Pt and that the other layers have the bulk composition. The first and second interlayer spacings are 2.23 +/- 0.03 angstrom and 2.21 +/- 0.03 angstrom respectively, corresponding to a contraction of 0.9% and 1.8% of the bulk value. The perpendicular buckling is 0.04 angstrom +/-0.05 angstrom in the top layer and 0.15 angstrom +/-0.04 angstrom in the second layer. The results are in full accordance with previous investigations of the physical and chemical properties of this surface.