A REVISED LEED DETERMINATION OF THE RELAXATIONS PRESENT AT THE (311) SURFACE OF COPPER

Low-energy electron diffraction (LEED) has been used to determine the structural relaxations present at the (311) surface of copper. Two sets of intensity vs energy curves were measured for normal incidence for 14 beams over a total energy range of 1932 eV. These data were compared with intensities calculated with the layer doubling method for a range of structural models, the comparisons being made with both the Zanazzi-Jona and Pendry R-factor schemes. Average values for the first and second interlayer spacings, and percentage changes from the bulk value, are found to be d1 = 0.96 +/- 0.02 angstrom (-11.9%) and d2 = 1.11 +/- 0.02 angstrom (+1.8%) respectively. These percentage changes are much closer to the theoretical relaxations (-12.2% and +4.4% respectively) calculated by Jiang et al. [Phys. Rev. B35, 7952 (1987)] than those indicated earlier by LEED for the Cu(311) surface using a 1978 data base.