An exceptionally stable hollow cage containing 20 scandium atoms and 60 carbon atoms has been identified. This Sc20C60 molecular cluster has a Th point group symmetry and a volleyball-like shape that we refer to below as "Volleyballene". Electronic structure analysis shows that the formation of delocalized π bonds between Sc atoms and the neighboring pentagonal rings made of carbon atoms is crucial for stabilizing the cage structure. A relatively large HOMO-LUMO gap (∼1.4 eV) was found. The results of vibrational frequency analysis and molecular dynamics simulations both demonstrate that this Volleyballene molecule is exceptionally stable.

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Recently, a stable hollow Sc20C60 cage with Th point group symmetry has been proposed, due to its volleyballlike shape called volleyballene. Here the structural and electronic properties for Sc20C60 cage with a europium atom are further studied based on density functional theory. The results give two stable low-lying Eu@Sc20C60 isomers, called cage-a and cage-b, respectively, which still retain the cage-like shape of Sc20C60 volleyballene. After a Eu atom is encaged into the Sc20C60 volleyballene, the HOMO—LUMO gaps decrease from 1.47 eV of the Sc20C60 cage to 0.46 eV of cage-a and 0.21 eV of cage-b. Due to the half-filled 4f-electron orbital states of the Eu atom, the two low-lying Eu@Sc20C60 isomers have net magnetic moments of 7μB. This study further provides the possible applications for the Sc20C60 volleyballene, and enriches the species of magnetic cage-like molecules, which provides more information for magnetic storage and magnetic control.

A stable core–shell Mg20B24 structure has been constructed and investigated using first-principles calculations. This molecule consists of a boron icosahedron core with an Ih symmetry and a pentakis dodecahedron shell composed of an intercalated boron icosahedron and magnesium dodecahedron. Frequency analysis shows that the molecule was static stable, and its highest frequency of 685.4 cm–1 corresponds to the powerful “breathing” mode of the B12 core, and the lowest frequency is 141.6 cm–1 due to the vibrations of the outer shell. The molecular dynamics calculations suggest that it is stable at about 1600 K. Results show that the molecule has a highest-occupied molecular orbital–lowest-unoccupied molecular orbital gap of about 1.07 eV. This molecule may be a promising hydrogen storage material. There presents a double-shell distribution of absorbed H2 molecules for this molecule, and ∼175 H2 molecules are adsorbed on Mg20B24, with the gravimetric hydrogen density reaching ∼32.1%.

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