Obviously, the presence of the O-vacancy and the location of the O-vacancy underneath the Ru nanorod have very little influence on the CO adsorption energies on the top layer sites. This follows the trend of the charge variation on the 1c and the 7a / 8a sites for the different Ovacancies, which are also negligible (see Table ), as expected for an efficient screening by the underlying metal layers. Comparing the CO adsorption energies on the two top-layer sites also shows that adsorption on the edge site is by about 0.25 eV more stable than on the terrace site, which can be understood from the lower Ru coordination at the edge site. The difference is, however, smaller than obtained in earlier calculations for CO adsorption on different metal surfaces, which showed a more pronounced difference of about 0.5 eV for adsorption on Pt terrace and step sites, respectively. This discrepancy may be attributed to the strain on the Ru nanorod induced by the support lattice, which changes the distance between Ru-1c and the neighboring Ru atoms in the terrace area from 2.70 Å to a range between 2.51 and 2.78 Å.