| First, a short introduction to the field of fullerenes, fullerites, fullerides and carbon nanotubes is given. Then, the structures of polymerised C60 fullerite and polymerised AC60 alkali fullerides (A = K, Rb or Cs) are discussed. A microscopic Landau theory is presented to account for the specific orientations of the polymer chains in these compounds. After calculating van der Waals and electrostatic interactions between C 60 molecules and alkali atoms, taking into account orientational and translational degrees of freedom, we conclude that the quadrupolar polarisability of the alkali ions is the key mechanism responsible for the alternating polymer chain orientations in KC60 and the equal polymer chain orientations in Rb- and CsC60. A second problem concerns the experimentally observed structural phase transition (the formation of a superstructure) in polymerised KC60 at approximately 60 K. As a mechanism, we suggest orientational charge density waves (small angular deviations of the valence charge distributions on the C60 molecules), indeed explaining the formation of a superstructure. The same mechanism also accounts for the experimentally observed metal-insulator transition in polymerised KC60 as we demonstrate by performing tight-binding band structure calculations. We find it necessary to take the three-dimensionality of a KC60 crystal fully into account. A fourth topic concerns C60 molecules encapsulated in a single-walled carbon nanotube, a so-called peapod. By treating the surrounding nanotube as a smooth carbonic cylinder but considering the full icosahedral symmetry of a C60 molecule, we calculate the crystal field of a C60 molecule due to the van der Waals interaction between the C60 molecule and the nanotube wall for various tube radii. We find a flipping of energy minima and maxima within the range 6 A--8 A. As a result, a satisfactory explanation of resonant Raman measurements on such compounds can be given. |
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