Formation of Metal-Encapsulating Si Cage Clusters

Abstract

We report the formation of a series of metal-containing hydrogenated silicon clusters using an ion trap. Mass analyses reveal that many types of transition metal ions $M^{+}$ ( $M=\mathrm{Hf}$, Ta, W, Re, Ir, etc.) react with silane $\left({\mathrm{SiH}}_4\right)$ to form dehydrogenated $M{\mathrm{Si}}_n^{+}$ cluster ions ( $n=14\mathrm{}$, 13, 12, 11, 9, respectively) as an end product, indicating that the metal atom is endohedral and stabilizes the Si polyhedral cage. This finding is confirmed by our ab initio calculation that ${\mathrm{WSi}}_{12}$ is a W-encapsulating ${\mathrm{Si}}_{12}$ cage cluster, and is very stable owing to both the electronic and the geometrical shell closures.