Role of Hydrogen in Dimerizaton of Aluminum Clusters: A Theoretical Study

We have used density functional theory to investigate how Al-13 cluster dimers can be formed with or without a bridging hydrogen. We have identified several stable dimers in which 0, 1, or 2 hydrogen atoms link two bare clusters together. Each of these structures can adsorb further H atoms in atop sites on the surface of the dimer. Additional dimers were identified with 3 and 4 H atoms linking the clusters but these are only stable in the multihydrogenated form. Reaction profiles for the formation of these dimers from a range of cluster and H atom combinations indicate that the dimer structures are energetically favored over the isolated clusters. This observation may have significant implications for the design of cluster-assembled materials.