Density functional studies on a novel double-shell fullerene C20@C60

Geometrical and electronic structures of the smallest potential double-shell fullerenes C20@C60 were studied by using Hartree-Fock and density functional theory (DFT) B3LYP methods. Two distinctly different highly endothermic but stable isomers are located; the fusiform one with D5d symmetry is 848.22 kcal mol−1 lower in energy than the spherical (Ih) one. Their frontier orbital, electrostatic potential as well as the electron affinity (EA) and the ionization potential (IP) were presented to give a comprehensive description of this novel endohedral system. The inter-shell interactions between C20 layer and C60 layer in C20@C60 are proved to be 'through-bond' and 'through-space' interactions for the fusiform isomer and spherical one, respectively.