Finally, considering adsorption on the interface (ii) site, the formation of the O-vacancy at the 1i site results in a significant increase of the negative charge on the Ru adsorption site (Figure ), comparable to that of an individual O-vacancy at the (ii) site (Figure ). Addition of an O-vacancy at the (ii) site, however, does not further increase the negative charge on this adsorption site, but changes it to a slightly positive value. This is at least partly related to the different adsorption sites in both cases, a (Ru-2a, Ru-6a) bridge site for the individual (ii) Ovacancy and a (Ru-4a, Ru-6a) bridge site for the (ii) O-vacancy in the 2VO vacancy cluster.