Ab initio calculations of multilayer relaxations of stepped Cu surfaces -: art. no. 115405

We present trends in the multilayer relaxations of several vicinals of Cu(100) and Cu(111) of varying terrace widths and geometries. The electronic structure calculations are based on density-functional theory in the local-density approximation with norm-conserving, nonlocal pseudopotentials in the mixed basis representation. While relaxations continue for several layers, the major effect is concentrated near the step and corner atoms. On all surfaces the step atoms contract inward, in agreement with experimental findings. Additionally, the corner atoms move outward and the atoms in the adjacent chain undergo a large inward relaxation. Correspondingly, the largest contraction (4%) is in the bond length between the step atom and its bulk nearest neighbor (BNN), while that between the corner atom and the BNN is somewhat enlarged. The surface atoms also display changes in registry of up to 1.5%. Our results are in general in good agreement with low-energy electron-diffraction data including the controversial case of Cu(511). Subtle differences are found with results obtained from semiempirical potentials.