Low-Energy Electron-Diffraction Intensity Calculations for Beryllium with a Realistic Crystal Potential

Abstract

The band-matching approach is used to calculate low-energy electron-diffraction intensity-voltage curves for the basal cleavage plane of beryllium. An approximation to the exact theory, made possible by the presence of strong inelastic scattering, enables these curves to be calculated very rapidly, for general angles of incidence and with a detailed nonlocal potential. The potential is constructed from first principles, includes thermal and inelastic-scattering effects, and has no adjustable parameters. Over a wide range of incident angles the calculated curves show marked agreement with recent experiments. A test of the sensitivity of the calculations to changes in the scattering potential parameters shows that the absolute intensity, rather than peak position or peak width, should be the best experimental probe of the scattering processes. A new approximation for core-valence exchange is used in the calculation and is described in an appendix.