Structural and electronic properties of metal-doped silicon clusters $M{\mathrm{S}\mathrm{i}}_n$s ($M=\mathrm{W}$, Zr, Os, Pt, Co, etc.) in a large size range of $8\le n\le 20$ are investigated via ab initio calculations. Different from a recent experimental suggestion that the metal atom is endohedral in $M{\mathrm{S}\mathrm{i}}_n$, we reveal that the formation of endohedral structure strongly depends on the size of the ${\mathrm{S}\mathrm{i}}_n$ cluster. Two novel structures of the chemically stable endohedral species are manifested. The suitable $M@{\mathrm{S}\mathrm{i}}_n$ building blocks of self-assembly materials vary in the range of $10\le n\le 16$. The thermodynamical magic numbers are found to coincide with the chemical magic numbers for five clusters.

• Received 2 July 2002

DOI:https://doi.org/10.1103/PhysRevLett.90.115506