Figure 5: Theoretical results for adsorption energies of the Pb layers.

(a,b) Adsorption energy map for first and second layer Pb atoms around the RTH cluster centre, overlaid with atomic positions for the topmost substrate layer and Pb. Green spheres correspond to Yb, red to In, orange to Ag and other colours to Pb atoms. Inset shows the interatomic distances between adsorbed Pb atoms (see text). (c,d) Side view of atomic structure for the substrate and Pb film. (e,f) Adsorption energies for selected sites as a function of distance from the surface. Adsorption energy curves for 2nd_1 (red) and 2nd_2 (green) sites in e were calculated with the absence of the underlayer, and the same curves in f are after the underlayer atoms are considered. The centre pentagonal sites in a (right) have the highest adsorption energy. We note that a repulsive interaction is expected between atoms adsorbed on centre pentagonal sites, shown in Fig. 5b. Therefore, these sites may be occupied partially. However, adsorption behaviour at these sites is ambiguous because of lack of information of exact atomic structure at the centre of the RTH cluster.