In the following, we will take a closer look into how the compounds adsorb on the considered surfaces, focusing on adsorbates that show a substantial variation in their adsorption behavior on these surfaces. First, we look at carbon monoxide, which offers little difference in adsorption energy between sodium metal and sodium chloride. Despite this slight difference in energetics, the adsorption of CO on sodium chloride occurs via a Na-O binding, in contrast to the Na-C binding on metallic sodium, which is well established for other metal surfaces . The different adsorption structures for CO and CO 2 are depicted in Fig. .