Dynamics of dissociative chemisorption of O2 on Cu(100) surface: A theoretical study

The dynamics of O-2 dissociative chemisorption on Cu(100) is studied by means of quasi-classical dynamics simulation making use of a 6-dimensional potential energy surface based on density functional theory (DFT) calculations. The sticking probability is found in reasonable agreement with experiment above 0.3 eV collision energy. However, theory fails at capturing the activated behaviour experimentally evidenced for lower energies. While molecular beam experiments exhibit an energetic threshold in the sticking curve, simulations show a high dissociation probability at collision energies below this threshold. Present calculations suggest that this discrepancy is due to dynamics governed by a direct dissociation mechanism steming from several barrierless reaction paths associated with an indirect dissociation mechanism governed by dynamic trapping. These direct and indirect components are strongly related to the structure of the PES questioning the reliability of the DFT calculations and the choice of the functional used. Beyond the question of the DFT accuracy, this theoretical work addresses the still open question of experiments/theory comparison for systems involving O-2 and metal surfaces such as Cu(100).