Hydrogenated Silicon Fullerenes: Effects of H on the Stability of Metal-Encapsulated Silicon Clusters

Ab initio calculations of H interaction on Si₁₂M, Si₁₈M₂ (M=Cr, Mo, and W), and Zr@Si₁₆ fullerene (f) show relatively weak binding of H in agreement with experimental results of H free Si₁₂M and Si₁₈M₂ clusters. Adsorption of H enhances sp³ bonding between the Si atoms, weakens the M-Si cage interactions, and leads to distortions in the cages. Si₁₂CrH₁₂ has 4μ_B magnetic moment in contrast to zero for Si₁₂Cr. Removal of the M atom leads to stable empty cages of Si₁₂H₁₂, f-Si₁₆H₁₆, and f-Si₂₀H₂₀ with large highest occupied–lowest unoccupied molecular orbital gaps of 2.5–3.0 eV, making them attractive for optoelectronic applications.