How Fast Do Microhydrated Al Clusters React: A Theoretical Study

Abstract

The dynamics of the first step of the reaction of small Alm clusters m = {3,13} with up to four water molecules has been studied. The first stage in the reaction, which may ultimately result in the production of H2, is the generation of a HAlmOH·(H2O)n−1 species, which can take place through transition states of the relay type, in which the water molecules may play different catalytic roles; namely, they can be involved directly in a Grotthuss-like mechanism by forming a relay bridge, or they may lower the saddle point energy by interacting with the molecules of the relay bridge. Rate coefficients have been computed with the inclusion of tunneling effects. The results indicate that the optimal configuration (the one giving the highest values of the rate coefficient for 50 K < T < 500 K) in the case of the Al3·(H2O)n system involves three water molecules in the relay bridge. In the case of the Al13 cluster, the two-water system is the most efficient. It is remarkable that Al3 delivers much higher rates tha...