Hydrogenation-induced structural evolution of small silicon clusters: The case of Si6Hx+

We present a theoretical study of a hydrogenation-induced geometry evolution of positively charged Si6Hx+ clusters. The structures can be categorized into distinct families according to the topology of the Si framework, in close analogy to the case of the neutral counterparts. However, the calculated formation energy as a function of x suggests that relative stability among the structural families significantly deviates from that of the neutral clusters around x∼6. We further present a molecular-orbital picture for the hydrogenation-induced structure transformation of both positively ionized and neutral Si6Hx clusters.