Intensities of low-energy-electron-diffraction beams from Be(0001)

The intensities of several low-energy-electron-diffraction (LEED) beams from a clean Be(0001) surface are measured as functions of incident-electron energy, azimuth, and angle of incidence. The resulting LEED spectra (intensities vs energy) of the specular and of two nonspecular beams are plotted for two different azimuth angles from 20 to 300 eV and every 2° in incident angle from 0° to 24°. Several of the nonspecular spectra are compared with the results of calculations done by means of a band-matching perturbation approach utilizing a suitable pseudopotential. The comparison shows encouraging agreement considering, in particular, the speed and simplicity of the computations. Attention is drawn to the fact that the intensities of nonspecular beams from the basal plane of the hexagonal-close-packed lattice depend on the way in which the structure is terminated at the surface, in contrast to the close-packed {111} face of the face-centered-cubic lattice, for which termination plays no role.