Small cobalt clusters encapsulated inside Si₃₀C₃₀ nanocages: electronic and magnetic properties.

We investigated the structural, electronic, and magnetic properties of small Co(n) clusters (n = 2-6) when they were endohedrally doped into Si₃₀C₃₀ nanocages using ab initio calculations based on density functional theory. Two different spin-polarized functionals based on the generalized gradient and local density approximations were used to characterize Co(n)@Si₃₀C₃₀. It was found that the Co(n) clusters encapsulated inside Si₃₀C₃₀ nanocages can form stable structures due to their significant binding energies. Among the various encapsulated clusters studied, the Co₄ cluster was the most stable in a Si₃₀C₃₀ nanocage. We also found that the magnetic moments of the clusters decreased during the encapsulation process due to substantial hybridization between the cobalt cluster and the Si₃₀C₃₀ nanocage structure, although the encaged Co₂ cluster presented somewhat different behavior. It was found that significant magnetic moments are induced in the wall of the nanocage, and that Co(n)@Si₃₀C₃₀ presents higher total magnetic moments than Co(n)@C₆₀.