Appendix 2:

For less than one monolayer coverage such that adatom clusters do not contact each other, the criteria governing the presence of clusters centered over hep sites (fault islands) and over fee sites (non-fault islands) are that mobile clusters are distributed on the surface sites according to a Boltzmann distribution (i.e. the cluster ensemble is in thermal equilibrium), and that the largest mobile cluster of size i is mobile if the time t _i it needs to exchange between fee and hep is smaller than the time t ₊₁ needed to add an additional atom to it. (The addition of one adatom to the largest mobile cluster decreases its mobility and causes the cluster one adatom larger than the largest mobile cluster to become stuck.) Thus, clusters larger than the largest mobile cluster will have a distribution identical to that for the largest mobile cluster. If P _hcp,i is the population of i size clusters that occupy hep sites and P _fcc,i is the population of i size clusters that occupy fee sites then P _hcp,i,/P _fcc,i = exp[(F _i,fcc-F _i,hcp)/kT]. It is this ratio that is measured in the STM observations. The data used to evaluate the free energies is described in detail in Ref. [A2]. Figure 4.A4 shows a comparison between the experimental data, closed square points; with this atomic model, full line. The authors of Ref. [A2] also used two other theoretical models: one based on the well-established...