Furthermore, it also contains the difference in energy for the removal of an O-atom (see Figure ). Splitting this up into separate contributions would be ambiguous, since depending on whether the O-removal would take place before or after restructuring the resulting numbers would be different. As illustrated in the reaction cycle in Figure . Obviously, in all cases the difference in interaction energy is the dominant contribution to the Ru-induced lowering of the O-vacancy formation energy. In many cases, the interaction energy is by about 2.0 eV more negative for the Ru/ZrO2-x system than for the Ru/ZrO2 system, leading to a corresponding stabilization of the O-vacancy by the Ru nanorod. In contrast, the structural contribution is generally rather low. This is particularly true for the Ru deformation energy ∆𝐸 𝑅𝑢 𝑑𝑒𝑓𝑜𝑟𝑚 , which except for few exceptions is below +0.1 eV.