Direct observation of nucleus of lithium in a C60 fullerene cage by neutron diffraction study

The nucleus of the Li+ as determined by neutron diffraction study was closer to the inner wall of the C60 fullerene cage than that of the center of its electron density. [Display omitted] •First direct observation of the nucleus of the metal of the endohedral fullerenes.•The nucleus of the Li+ was closer to the inner wall of the C60 fullerene cage.•Hyperconjugation interaction would arise between the Li+ orbital and the C60 cage. The nucleus of the Li+ in a C60 fullerene by a neutron diffraction study was closer to the inner wall of the fullerene cage than that of the center of its electron density, and the hyperconjugation interaction would arise between the vacant Li+ orbital and the π orbitals of the hexagonal moiety of the C60.