Reactivity of molecular oxygen with aluminum clusters: Density functional and Ab Initio molecular dynamics simulation study

Dissociative adsorption of molecular oxygen (O-2) on aluminum (Al) clusters has attracted much interest in the field of surface science and catalysis, but theoretical predictions of the reactivity of this reaction in terms of barrier height is still challenging. In this regard, we systematically investigate the reactivity of O-2 with Al clusters using density functional theory (DFT) and atom-centered density matrix propagation (ADMP) simulations. We also calculate potential energy surfaces (PESs) of the reaction between O-2 and Al clusters to estimate the barrier energy of this reaction. The M06-2X functional gives the barrier energy in agreement with the one calculated by coupled cluster singles and doubles with perturbed triples (CCSD(T)) while the TPSSh functional significantly underestimates the barrier height. The ADMP simulation using the M06-2X functional predicts the reactivity of O-2 with the Al cluster in agreement with the experimental findings, that is, singlet O-2 readily reacts with Al clusters but triplet O-2 is less reactive. We found that the ability of a DFT functional to describe the charge transfer appropriately is critical for calculating the barrier energy and the reactivity of the reaction of O-2 with Al clusters. The M06-2X functional is relevant for investigating chemical reactions involving Al and O-2. (c) 2016 Wiley Periodicals, Inc.