ELECTRON-DENSITY AND STRUCTURE OF THE (1X2)-AU(110) SURFACE STUDIED BY HE-BEAM SCATTERING

The (1x2)-Au(110) surface has been studied using He-beam scattering with time-of-flight detection. The experiments included measurement of the diffraction pattern and the specular intensity as a function of azimuthal angle of incidence; the latter curve is found to be highly structured. The data have been modeled using the local-density approximation to calculate the charge distribution in atoms, and treating the He-surface potential as a superposition of pseudopairwise terms. The diffraction pattern and azimuthal data can be well fitted using close-coupled channel calculations and varying only three parameters, giving confidence that the calculated electron density is accurate. It is found that the peak-to-peak corrugation of the 10(-3) angstrom-3 isoelectron density surface is almost-equal-to 1.2 angstrom, showing a substantial smoothing with respect to the corrugation of 1.55 angstrom found when superposing the calculated free atomic densities. In addition we have examined the sensitivity of the model calculations to geometric structure. They are consistent only with the expected missing row structure, and yield the separation between the first and second layers with an accuracy of 6%.