Systems Studied and Adsorption Energies

In Fig. 7, 25 relevant adsorption configurations, taken from the 531,441 that are possible for the environments that an atom can have on the surface, are shown. The corresponding adsorption energies are summarized, as illustrative examples, in Table 2 for the 

It is interesting to compare different physical situations which can be expected as a consequence of the energies involved in the configurations analyzed. Let us start by considering configurations 

Energy differences (eV) associated with the deposition of an atom in the enviromnents represented in Fig. 7 for the adsorption systems considered in this work. (Reprinted from Ref [16], with permission from the the American Chemical Society.) 

Configurations 19 and 20 are meaningful when considering adsorption at step sites. In these cases, the data in Table 2 indicate that upon adsorption on Pt steps, Ag and Au atoms will tend to avoid the presence of neighboring homoatoms. This fact is no longer im-expected, since both Ag and Au exhibit an important compressive surface stress when adsorbed on Pt. On the other hand, in the remaining systems, the adatoms would prefer to adsorb beside other adatoms. 

Configurations 21-23 represent the environment of the three kinds of kink sites that an atom can find on the surface. By comparing configurations 20 and 22 for all systems, one notices that for the systems Ag/Au, Ag/Pt, and Au/Pt adsorption onto kink sites (configuration 22) is favored as compared with step decoration (configuration 20), whereas for the systems Au/Ag, Pt/Ag, Pt/Au, Au/Pd, and Pd/Au the growth of a monodimensional phase at step sites should be preferred (configuration 20). 

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