Structure and Stability of a Trefoil Leaf Motif of Metal-Doped Silicon and Germanium Clusters: M3@E20 with E = Si and Ge and M = Fe, Ru, and Os.

The first trefoil leaf-shaped cluster, a novel structural motif, was discovered by quantum chemical computations using density functional theory methods for both binary M3@E20 silicon and germanium clusters in which a metallic M3 cycle is encapsulated within a D3h Si20 or Ge20 cage. The triatomic transition metal Fe3, Ru3, and Os3 cycles exhibit a suitable size to be placed inside both Si and Ge cages and satisfy electronic conditions, which thermodynamically stabilize the mixed clusters. Stabilizing orbital interactions between the M3 cycle and D3h E20 cage crucially contributes to the high stability of the resulting M3@E20 trefoil cluster. The novel trefoil leaf-shaped clusters can be used as building units to create different nanoassemblies.