Thus, a systematic investigation of the CO interaction with TMs and its possible dissociation would not only allow the discovery of the key, acting descriptors unfolding the physicochemical properties of TM surfaces and set a predicting basis for complex systems, e.g. TM nanoparticles and bimetallic structures . It could also drive the description of single-atom alloys, which have become a hub of research in the recent years . Such an understanding could be gained by means of Surface Science techniques , yet experimental methods suffer from limitations and inaccuracies, e.g. having the need of using wellcharacterized single-crystal metal surfaces, a ultra-high vacuum chamber while controlling the dose of CO, and the unavoidable acquirement of mean, average information of all the molecules and active sites present on the sample. A suitable alternative to gain molecular and site-specific atomistic information is the use of accurate atomistic simulations. Within this Computational Surface Science field, Density Functional Theory (DFT) applied to surface slab models has excelled over other approaches, being an excellent compromise in between computational cost and accuracy.