Smallest Fullerene C20 Research Articles

Prediction of pure carbon crystals with intrinsic antiferromagnetism: polymerized from C20 fullerenes.

Pure carbon materials with magnetic properties have attracted considerable research interest due to their advantages over traditional magnetic materials. Nevertheless, such materials are exceedingly rare. Disrupting the Kekulé valence structures in carbon materials potentially leads to the emergence of magnetism. In this study, using first principles calculations, we developed a range of pure carbon allotropes derived from the smallest fullerene C20 which potentially disrupts the Kekulé valence structures after polymerization. The results indicate that some of the allotropes disrupting the Kekulé valence structures exhibit intrinsic antiferromagnetic ordering, and the magnetism originates from the presence of isolated three-fold coordinated C atoms. The other allotropes adhering to the Kekulé valence structures show non-magnetism with all three-fold coordinated C atoms forming dimers. In all magnetic polymers, magnetism arises from unpaired electrons on the isolated three-fold coordinated carbon atoms, with magnetic moments of about 0.40μB at these sites. The adsorption of dopant atoms can significantly alter the magnetic properties of polymers, for instance, the C20-71 polymer with Immm symmetry undergoes a transition from non-magnetic to anti-magnetic ordering upon adsorption of hydrogen atoms. Electronic calculations indicate that these polymers display a range of electronic properties, encompassing both metallic and semiconducting characteristics. Notably, certain magnetic phases exhibit superhard properties, with the hardness value exceeding 40 GPa. This study presents a potential method for designing magnetic carbon materials. Specifically, certain compounds address the gap in magnetic superhard materials composed of light elements, and can be utilized in the field of spintronics where traditional superhard materials are unsuitable.

DFT Study on the Interaction of the Smallest Fullerene C20 with Lithium Ions and Atoms

The smallest fullerene C20 with positive electron affinity is considered to be a new organic nano-electronic material. The binding structures and electronic states of lithium ions and atoms (Li+ and Li) trapped on the surface of C20 have been investigated by means of density functional theory (DFT) calculation to elucidate the nature of their interaction. It was found that a Li+ can bind to only one site of C20. This is, specifically, on top of the site where Li+ binds to the carbon atom of C20. On the other hand, in the case of a Li atom, two structures were obtained besides the on-top structure. One was pentagonal structure which included a Li atom on a five-membered ring of C20. The other was a triangular structure in which the Li atom bind to the the carbon–carbon bond of C20. Finally, the nature of the interactions between Li ions or atoms and the C20 cluster was discussed on the basis of theoretical results.

Density Functional Theory (DFT) Study on the Addition of Hydroxyl Radical (OH) to C20

The radical addition to the smallest fullerene C20 has been investigated by means of density functional theory (DFT) method in order to elucidate the radical scavenge mechanism of fullerene. The OH radical was examined as an organic radical because the radical has a high reactivity. The DFT calculation showed that the OH radical binds directly to the carbon atom of C20 and a strong C-O bond is formed. The binding energies of the first addition of OH radical were calculated to be 85.2 kcal/mol at the B3LYP/6-311G(d,p) level of theory. In the second radical addition, the binding energy of OH to C20(OH) was 91.5 kcal/mol. The unpaired electron was distributed widely over the C20 surface in the C20(OH) complex.