As a last point, we briefly compare with CO adsorption on PdAg(Ag(111) or PtAg/Ag(111) surface alloys, which were prepared by deposition of Pd or Pt on a Ag( ) substrate . Also these samples differ from the Pd supported surface alloys by the different lattice constant, which for pseudomorphic films result in very different strain effects, the different vertical ligand effects (Pd-Ag instead of Pd-Pd interaction), and in particular by their much higher tendency for intermixing.