3d transition metals: Which is the ideal guest for Sin (n=15,16n=15,16) cages?

The configurations, stability, and electronic structures of Si15 and Si16 cages with encapsulated 3d transition metal atoms, M@Si15 and M@Si16 (M = Sc, Ti, V, Cr, Mn, Fe, Co, or Ni), have been investigated within the framework of all-electron density functional theory. The results show that Ti@Si16 and Ti@Si15 have the largest embedding energies in this series and relatively large HOMO–LUMO gaps. This suggests that the titanium atom is an ideal guest for Sin (n=15,16n=15,16) cages as far as stability is concerned. The Mn atom is found to have a large spin moment even when encapsulated, while the spin moments of Ti, Cr, Fe, and Ni are entirely quenched upon doping into the Si15 and Si16 cage clusters.