For Pt7Ge2 and Pt7Ge2C2, the GM isomers are substantially more stable than the LM1 and LM2 isomers, and therefore dominate the cluster ensemble (P700K > 98%). All Pt atoms are exposed in the cluster surface layer, and as might be expected, the thermodynamically most stable geometries with one ethylene adsorbed are all based on the GM for Pt7Ge2, and have all Pt atoms in the surface layer.