A systematic theoretical study of the equilibrium geometries and total energies of Cr encapsulated in Si clusters reveals that $\mathrm{Cr}{\mathrm{Si}}_{12}$ is more stable than its neighbors. The origin of this enhanced stability is consistent with the 18-electron sum rule commonly used in the synthesis of stable chemical complexes, and may provide a criterion for a systematic search of magic numbers in metalloinorganic clusters. The $6{\mu }_{\mathrm{B}}$ magnetic moment of the caged Cr atom, the largest among the $3d$ transition metal atoms, is completely quenched. This effect of caging on the properties of transition metal atoms may lead to the synthesis of novel cluster based materials.

• Received 13 September 2001

DOI:https://doi.org/10.1103/PhysRevLett.89.016803