Effect of charge state on bonding in fulleride polymers

Both two- and one-dimensional single bonded fulleride polymer phase have been investigated theoretically using the Huckel model. Parameters for the sp(3) hybridized carbon atoms forming the bonds have been found by fitting the energy spectrum and bond orders of the bonding atoms of a single bonded C-60 dimer to the results of VEH calculations on model systems of the polymers. Our calculations strongly support previous results, that the two-dimensional polymeric phase is stabilized when a charge of four electrons per C-60 molecule is applied. The one-dimensional single bonded chain is stable when the C-60 molecules are at least doubly charged, which is in agreement with experimental observations for Na2RbC60 (three electrons per C-60 molecule).