Multilayer relaxations in the Cu(311) surface determined by leed crystallography

Abstract

We have reanalyzed an experimental dataset of 8 symmetrically non-equivalent LEED beams obtained for normal incidence on the stepped (311) surface of copper [Surface Sci. 72 (1978) 744]. The analysis allows for multilayer relaxations up to three layers deep into the crystal; we find clear evidence for a contraction of the first interlayer distance, and a smaller expansion for the second interlayer distance. We have used three different, but commonly used, R-factors, and they show some differences in structural conclusions. The average interlayer distances and percentage changes from the bulk values are: d 1 = 1.01 ±0.03 A ̊ (−7.3%), d 2 = 1.13 ± 0.01 A ̊ (+ 3.7%), d 3 = 1.09 ± 0.01 A ̊ (0.0%) . These results reinforce the concept of multilayer relaxations in open surfaces. The magnitude of the change found here in the top layer spacing (−7.3%) appears significantly less than other values reported for (311) surfaces of fcc metals, both from theory (−12.2%) and from LEED analyses for aluminum (−13.3%) and nickel (−15.9%).