Structural and electronic properties of polymeric fullerene chains

Properties of polymeric fullerenes are studied theoretically using a semiempirical model that treats only the π electrons explicitly but allows for lattice relaxations. Both neutral and charged systems are studied, and both the isolated ${\mathrm{C}}_{60}$ molecule as well as the polymer. In agreement with experiments, the model predicts the elongation of certain intraball bonds upon polymerization as the most significant structural relaxation. This is found both for the neutral and the charged system. For the latter, we observe symmetry reductions, and it is suggested that polaronlike distortions or charge-density waves may act as charge carriers. The distortions are predicted to induce extra phonon modes that should be observable experimentally.