Figure 4

afor the (2 × 2)/(3 × 3) Pb/Cu(111) structure, and the plotted plane is vertical to the Cu(111) surface and along the longer diagonal of the parallelogram pattern (in Fig. 2a); b the same as a, but the plotted plane is parallel to the Cu(111) surface and crossing the Pb atoms in the second layer. Solid lines (red area indicates highest value) and dashed lines(blue area indicates lowest value) correspond to ∆ρ > 0 and ∆ρ < 0, respectively. The white area corresponds to ∆ρ = 0