Low-energy-electron-diffraction study of multilayer relaxation on a Pb{311} surface

Multilayer relaxation on clean Pd{311} has been determined by analysis of low-energy-electron-diffraction intensity data collected from a sample at -140° C. The results, in terms of changes dik from the bulk value dbulk (1.485) of the interlayer spacing dik between layers i and k, are as follows: d12=(-0.210.03) or (-14.12.0)% of dbulk, d23=(-0.030.03) or (-2.02.0)% of dbulk, d34=(-0.010.05) or (-0.73.4)% of dbulk, and d45=(0.080.05) or (+5.44.0)% of dbulk. Since the {311} surface has only one mirror line, parallel relaxations along the mirror line (the x direction) are possible and indeed found. The changes along x are s12x=(0.080.05) or (+3.01.9)% of the bulk value 2.626, and s23x=(-0.050.05) or (-1.91.9)% of the bulk value. The contraction of d12 is comparable in magnitude to that found on {311} surfaces of other face-centered-cubic metals, in contrast to the results obtained earlier on Pb{110}, Pb{001}, and Pb{111}. However, as on these low-index surfaces, the relaxations extend more deeply into the bulk than on surfaces of other fcc metals. © 1991 The American Physical Society.