Ni clusters: Structures and reactivity with D2

Abstract

We report the results from a theoretical investigation of the structures and reactivity of various isomers of Ni clusters in the size range from 4 to 13 atoms. The geometries of the clusters were optimized using binding energy values calculated by the corrected effective medium (CEM) theory. Two different potential energy surfaces were used to describe the interaction between D₂ and the Ni clusters. The first used the form and parameters that were determined in the study of H₂ dissociative chemisorption on Ni surfaces, while both used atomic positions appropriate to the clusters, the second used the same form but determined the parameters by comparison to CEM values of the H/Ni₁₃ interaction. Using these PES, we investigated the dissociation dynamics of D₂ on Ni_N (N=4–13) clusters by classical trajectory techniques. We found that: (1) for clusters of size less than Ni₉ , the rate constants varied strongly with cluster size; and (2) for all size clusters, the rate constants were very sensitive to different isomers. This isomeric variation of the rate constant is discussed in terms of various structural features in different isomers, a number of which do not have any analogy in the dissociative chemisorption on low Miller index surfaces.