Dissociation mechanism of ethylene molecules with a Ni cluster:ab initio molecular-dynamics study

The dissociation reactions of ethylene molecules on a Ni cluster are examined by means of ab initio molecular-dynamics simulations. The dissociation reactions of hydrogen atoms are observed at a rate of about 20 ps -1 in our simulations. While more than half of the dissociated hydrogen atoms exist around the Ni cluster, the rest form hydrogen molecules. We also calculate the activation energy for the dissociation reaction of a hydrogen atom to be about 0.52 eV, which corresponds to a rate of only about 0.1 ps -1. To explain the large difference between these reaction rates, we investigate adsorption energies of the ethylene molecule on the Ni cluster. As a result, we clarify that the adsorption energy is more than 1.5 eV, which is three times greater than the activation energy for the hydrogen dissociation. Therefore, the adsorption energy is responsible for the increase of the rate of the dissociation reaction