ELECTRON PROPAGATION IN ORIENTATIONALLY DISORDERED FULLERIDES

We study the electronic spectrum for doped electronic states in the or ientationallY disordered M3C60 fullerides. Momentum-resolved Green's f unctions are calculated within a cluster-Bethe-lattice model and compa red with results from calculations on periodically repeated supercells containing quenched orientational disorder. Despite the relatively st rong scattering from orientational fluctuations, the electronic states near the Fermi energy are well described by propagating states charac terized by an effective Bloch wave vector and a mean free path l almos t-equal-to 20 angstrom. The effective Fermi surface is calculated in t his model. This differs from that previously calculated for the orient ationally ordered crystal, but is relatively well described within a d isorder-averaged virtual-crystal Hamiltonian, which we derive.