Geometric and Electronic Structures of Vanadium Sub-nano Clusters, Vn (n = 2-5), and their Adsorption Complexes with CO and O2 Ligands: A DFT-NBO Study

In this study, electronic structures of ground state of pure vanadium sub-nano clusters, Vn (n=2-5), and their interactions with small ligands for example CO and triplet O2 molecules are investigated by using density functional theory (DFT) calibration at the mPWPW91/QZVP level of theory. The favorable orientations of these ligands in interaction with pure vanadium sub-nano clusters were determined. Multiplicities of these pure clusters are triple, doublet, singlet and doublet for dimer, trimer, tetramer and pentamer, respectively. While the CO molecule is associatively adsorbed on vanadium clusters, triplet O2 is dissociated over adsorption. Primary and secondary hyper-conjugation concepts have been employed to show stabilization of vanadium oxide complexes. Natural bond orbital (NBO) and natural resonance theory (NRT) analysis revealed that trimer, tetramer and pentamer clusters are relatively delocalized and have some resonance structures.