Dissociation and recombination rate constants for CN on Cu and Ni group transition metal surfaces

We report dissociation and recombination reaction rate constants for CN on the fcc(111) surfaces of Ni, Pd, Pt, Cu, Ag and Au from molecular dynamics simulations employing our normalized bond index-reactive potential functions (NBI-RPF). The Arrhenius pre-exponentials for recombination of CN on these surfaces are about three orders of magnitude greater than the dissociation pre-exponentials. On the series of metals considered herein, the reaction energetics favor dissociation on the more active metals and favor recombination on the least active metals. However, the differences in the pre-exponentials of nearly a factor of 103 express the tendency of the reaction entropy to favor the recombination on the surfaces investigated. We also discuss the implications of these results in terms of the thermodynamics of the surface reactions.