Anomalous multilayer relaxation on a Cu{331} surface

Three independent theoretical studies of the multilayer relaxation on a Cu{331} surface had reported a sequence of layer contractions and expansions different from that expected and found on other stepped surfaces of metals with three atom rows per terrace. A quantitative low-energy electron diffraction analysis of Cu{331} finds a 13.8% contraction of the first interlayer spacing with respect to the bulk value (0.829 Angstrom), in fair agreement with the theoretical results, and very small relaxations of the deeper interlayer spacings. The signs of these relaxations do not reproduce exactly the theoretical predictions, but their small magnitudes allow the conclusion that the present experiment agrees with the earlier theories within the experimental error bars.