Formation of metal-encapsulating Si cage clusters

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 = Hf. Ta, W, Re, Ir, etc.) react with silane (SiH4) to form dehydrogenated MSin+ cluster ions (n = 14, 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 nb initio calculation that WSi12 is a W-encapsulatine Si-12 cage cluster, and is very stable owing to both the electronic and the geometrical shell closures.