First-principles studies of isomerization processes of silicon clusters

The coexistence of a large number of isomers is one of the defining properties of nanoclusters. Here we report first-principles calculations of activation energies of silicon isomer transformations using a method for constructing low-energy isomers. We find that isomers form distinct classes. Within a class, intraconversion of a cluster is mediated by low-barrier bond switches in the interior. Interclass conversion requires high-barrier bond breaking in the outer ring structure. The results are consistent with experimental measurements and they have implications for theoretical searches of low-energy cluster structures.