In this case, there is some variation in the charge on the Ru atoms interacting with CO upon varying the O-vacancy position (Figure ), but this seems to be too small to significantly affect the trend in the CO adsorption energy. Note that the increase in electron charge on the Ru adsorption site when going to the 1VO(7i) system is mainly due to a change in Ru adsorption site, from Ru-2a/Ru-6a to a Ru-2a/Ru-3a bridge site, while the charges on the different Ru surface atoms remain almost constant. Finally, the data in Figure indicate that the changes of the charge on the support, the Ru nanorod and CO upon CO adsorption are generally small, significantly less than for CO adsorption on the interface (i) site. Hence, the net charge transfer to the CO, into the 2* orbital and from the 5 orbital of CO, is much less. Only for the 1VO(7i)