Electronic structure of metallic rhombohedralC60polymers

Abstract

We report electronic structures and stabilities of rhombohedral ${\mathrm{C}}_{60}$ polymers by using the local spin-density approximation in the framework of the density-functional theory. Owing to hybrid networks of ${\mathrm{sp}}^2$-like (threefold coordinated) and ${\mathrm{sp}}^3$-like (fourfold coordinated) carbon atoms, the electronic structures of these polymers are considerably different from that of a face-centered cubic (fcc) ${\mathrm{C}}_{60}.$ We find that polymerized structures attained at the double bonds are semiconducting whereas polymerized structures attained at single bonds are metallic. Significant overlap of the wave function in the space among three adjacent ${\mathrm{C}}_{60}$ causes the metallic behavior on the latter polymers. We also find that the stacking ordering strongly affects the conducting properties of the metallic polymers. Despite substantial density of states at Fermi level, the ${\mathrm{C}}_{60}$ polymers do not exhibit any magnetic ordering. Total energy calculations show that the metallic ${\mathrm{C}}_{60}$ polymers have higher total energy than the semiconducting ${\mathrm{C}}_{60}$ polymer phases.