Energetics and Electronic Structure of Na-Doped Rhombohedral C60 Polymers

Based on a first-principles total-energy calculation, we studied the energetics and electronic structure of a Na-doped rhombohedral C-60 polymer. The intercalation of Na atoms into the interstitial sites of the C-60 polymer studied here is an exothermic process with an energy gain of about 1 eV per Na atom. A detailed analysis of the polymer energetics revealed that the tetrahedral interstitial site is favorable as an intercalation site because of the strong Coulombic interaction between Na and C-60. The electronic structure of the NaxC60 polymers are metallic in nature with a partially filled electronic energy band at the Fermi level.