Hyperfine coupling of endohedral fullerene Sc@C82

The hyperfine coupling of the endohedral metallofullerene, Sc@C$_{82}$, which is a candidate qubit for quantum computing, has been investigated theoretically and experimentally. Using density functional theory (DFT), we have systematically studied the molecular structures and energetics of nine isomers of C$_{82 }$and Sc@C$_{82}$ fullerenes. DFT predicts that the most stable isomer has $C_{2v}$ symmetry with the Sc atom lying off-centre along the $C_{2 }$ symmetry axis and forming partially covalent bonds with a carbon hexagonal ring of the fullerene cage. The hyperfine couplings between the unpaired electron spin and the Sc and C atoms have been calculated and compared to the electron spin resonance (ESR) spectra. The experimental isotropic hyperfine coupling constants confirm the $C_{2v}$ symmetry predicted for the ground state isomer. Furthermore, the calculated anisotropy of the hyperfine coupling tensor is in good agreement with low temperature experimental measurements. www.nanotech.org