IONIC METAL KXC60 - COHESION AND ENERGY-BANDS

Microscopic total-energy electronic-structure calculations for K(x)C60 show that solid C60 weakly bonded via van der Waals forces is transformed upon potassium doping into a strongly condensed ionic metal in which both Madelung and kinetic energies contribute to its large cohesive energy and bulk modulus. We also find that K doping induces lattice contraction which results in nonrigid energy-band modification. The Fermi level for K3C60 is found to be located close to a peak of the density of states.