The PtAg/Ag1L/Pt3L surface alloys with a single Ag sublayer are noticeable more stable (more negative H) than the PtAg/Pt4L surface alloys. In Figure , the first / last points correspond to the values of the Pt/Ag1L/Pt4L and the Ag2L/Pt3L systems, respectively. In this case, we find pronounced deviations from a strictly linear increase in the formation enthalpy, with almost constant values up to n = 4, followed by a slow increase. Actually, it looks like that there is a minimum at Pt = 3 /9. Reasons for this very different behavior, also compared to the PtAg/Ag2L/Pt2L system, can only be speculated upon in the moment. Also for the surface energy we find almost constant values for the Pt1 monomer up to the Pt4 tetramer (x  0.55) (Table ).