Covalent container compound: Empty, endohedral, and exohedralC28complexes

Results from quasidynamical local-density simulations on a small fullerene complex (${\mathrm{C}}_{28}$), three endohedral complexes (${\mathrm{C}}_{28}$@C, ${\mathrm{C}}_{28}$@Zr, and ${\mathrm{C}}_{28}$@Ti), a C atom bound to the corner of the ${\mathrm{C}}_{28}$ molecule, and ${\mathrm{C}}_{28}$ ${\mathrm{H}}_4$ are presented. This molecule forms spontaneously from a 29-atom diamond crystallite and, under proper circumstances, is a covalent container compound. Upon encapsulation of a Zr atom, 12.6 eV of energy is liberated leading to an unreactive closed-shell ${\mathrm{C}}_{28}$@Zr molecule. The open-shell structure of the empty molecule leads to a reactive yet relatively stable building block which might be useful for synthesis of new metastable forms of carbon-based materials. Electronic structures, ionization energies, electron affinities, equilibrium geometries, and bare Hubbard U parameters are presented.