Electronic structure and electric quadrupoles of a polymerized chain in solid AC60

We use a simplified Slater–Koster tight-binding approach and analytical angular dependences of three t1u wave functions of C60− in order to calculate one-dimensional electronic bands and electronic density distribution in polymerized alkali fullerides AC60 (A=K, Rb, Cs). We find that the polymerization leads to the appearance of electric quadrupoles on the C60− molecular ions and the conduction electron density is concentrated at the C60− equator in agreement with NMR data. We analyze inter- chain interactions and find that the crystal field potential energy of a polymer chain is minimized when it is rotated at ±45° around the orthorhombic a axis.