INTRAMOLECULAR CHARGE DISPROPORTIONATION AND THE BAND-STRUCTURE OF A(3)C(60) SUPERCONDUCTORS

Realistic electronic model calculations provide convincing evidence fo r intramolecular charge disproportionation of the LUMO (lowest unoccup ied molecular orbitals) band structure in the <Fm(3)over bar m> family of A(3)C(60) (A = K, Rb, Cs) superconductors. The conventional LUMO b and splits into three similar subbands showing an overall occupied ban dwidth of 1 eV and a steep decrease of the density of states at the Fe rmi level when the band population deviates from half filling. The dis proportionation effect results also in nonzero Jahn-Teller distortions , inhomogeneous charge distribution among carbon atoms, and low freque ncy reorientation modes of Jahn-Teller distortions on each fullerene s ites.