BAND RECONSTRUCTIONS OF KXC60 CAUSED BY THE COOPERATIVE JAHN-TELLER EFFECT

Band-structure calculations are performed in the framework of an exten ded Su-Schrieffer-Heeger model. Besides the intramolecular electron tr ansfer, we introduce the pi-electron hopping between the nearest neigh bor molecules in a crystal. The band structures of solid KxC60 (x=1,2, 3,4) and the cooperative Jahn-Teller distortions of Ceo molecules are calculated self-consistently. According to our results, K2C60 and K4C6 0 appear to be semiconducting with a small Jahn-Teller gap at the. Fer mi level. The shifts of Fermi level depend nonmonotonically on x, and the conduction bandwidth changes strongly upon doping.