From the perspective of coking effects on these model catalysts, one of the main conclusions from the ISS studies is that that the substantial post-750K-heating and post-TPD reductions in the numbers of strong Pt-associated C2D4 binding sites for Ptn/alumina, are not simply due to carbon sterically blocking Pt binding sites, as was previously noted for the case of Pt4/alumina. Nonetheless, carbon atoms clearly have large effects on both C2D4 binding sites and the thermal stability of the samples in repeated TPD runs (Figs. 1, 2, 5 and 6). Therefore, DFT was used to probe the effects of both Ge and carbon addition to small Ptn/alumina.