First principles study of small cobalt clusters encapsulated in C60 and C82 spherical nanocages

► The encapsulated Con clusters inside C60 (Ih) and C82 (C2v) cages, except Co7@C60, are energetically favorable. ► The encapsulation does not change significantly the structure of the enclosed clusters. ► The magnetic moment of the encapsulated clusters reduces due to a stronger Co-C hybridization for the larger clusters. ► It is found that for all complexes, additional peaks contributed by the Con atomic orbitals appear in the HOMO-LUMO gap (Eg) of the host fullerene.