Hybrid DFT and hyper-GGA DFT studies of the CO adsorption on Pt nanoclusters: Effects of the cluster size and better CO LUMO description

CO adsorptions on six model Pt nanoclusters were studied using the B3LYP, BMK and M05-2X methods. BMK and M05-2X gave a better unbound description of CO 2π∗ LUMO. The B3LYP results show no observable preference as reported earlier in other calculations. For BMK, the CO prefers to adsorb on top site except for Pt10-6-3 and Pt9-9-9. For M05-2X, top-site preference exists in the two-layer Pt10-6, Pt19-12 and the three-layer Pt9-9-9, but does not exist in other three-layer Pt clusters. Although BMK and M05-2X give the better LUMO of CO molecule, the poor description of the Pt band gap may cause problems in the site preference when the size increases.