Hence, theory predicts that once acetylene forms on the Pt4Ge cluster, regardless of the isomer, it will always dehydrogenate, though higher-energy isomers will dehydrogenate at lower temperatures, some with dehydrogenation barriers less than 1 eV. This prediction is consistent with the observation that no intact acetylene desorption is ever seen for Pt4Ge/alumina in the experiments (Fig. ). Thus, in ethylene TPD (and in the ethane-to-ethylene reaction), we predict that Ge addition largely, but not completely, suppresses carbon deposition, such that in repeated TPD cycles (or long reaction times) the clusters will slowly all become coked by at least a pair of carbon atoms, with the LM' isomer serving as a gateway to coking.