Enhanced multilayer relaxation at high-index stepped Cu surfaces

Multilayer relaxation at high-index Cu(hkl)(hkl=511, 320, and 410) stepped surfaces were determined by the first-principles all-electron full-potential linearized augmented plane-wave method within the framework of the local-density approximation and the generalized gradient approximation. The calculated relaxation of the interlayer distances, obtained by a geometry optimization procedure that minimizes the force on each atom, were compared with low-energy electron-diffraction (LEED) analysis of experimental data. In the case of Cu(511), the calculated results are in good agreement with the LEED analyses. On the other hand, for Cu(320) and Cu(410), there are large differences that may be understood from the fact that the LEED analyses of experiments consider up to only three or four layers from the surface, and that whereas even the fifth or sixth layers show large relaxation in our calculations, our results suggest a reanalysis of the LEED data with the inclusion of more layers.