When the Ge concentration is further increased, in Pt 4 Ge 3 , the most stable configuration corresponds to unbound ethane. Furthermore, neither III nor IV isomers, constituting about 20% of the population, are able to bind ethane. Nevertheless, the two lowest-energy isomers of Pt 4 Ge 3 do bind ethane, leading to the configurations shown in Fig. , where one C-H bond is activated, and elongated to 1.13 Å. These results suggest a reduction in the ability of these clusters to activate ethane as the Ge content in the cluster increases. For Pt 4 Ge 4 , the majority of the populated isomers do not bind ethane, and the cluster can be considered rather catalytically inactive. Only a tiny portion of ethane (6% of population) binds to the Isomer II, leading to the configuration 3.