Ab initio study on the kinetics and mechanisms of the formation of Agn (n = 2-6) clusters

The CCSD(T)/11e-RECP//MP2/11e-RECP method was used to explore the potential energy surfaces (PESs) of the formation of Agn (n = 2-6) clusters. Two kinds of reaction mechanisms were revealed in the formation of Agn clusters, the association mechanism for the formation of Ag2, Ag5, and Ag6 clusters and the association-isomerization mechanism for the formation of Ag3 and Ag4 clusters. Based on the canonical transition state theory, the calculated rate constants of the formation of Agn clusters displayed an odd-even effect: the rate constants of formation of Agn clusters with odd number were larger than those with even number. The rate constant of formation of Ag4 was the lowest, whereas that of Ag5 was the highest among Agn (n = 2-6) clusters. The formation of Ag4 was the most difficult step in the aggregation process of the silver clusters. The formation of Ag4 may be related with the critical point in the silver aggregation process.