Microscopic total-energy electronic-structure calculations for ${\mathrm{K}}_{\mathit{x}}$${\mathrm{C}}_{60}$ show that solid ${\mathrm{C}}_{60}$ weakly bonded via van der Waals forces is transformed upon potassium doping into a strongly condensed ionic metal in which both Madelung and kinetic energies contribute to its large cohesive energy and bulk modulus. We also find that K doping induces lattice contraction which results in nonrigid energy-band modification. The Fermi level for ${\mathrm{K}}_3$${\mathrm{C}}_{60}$ is found to be located close to a peak of the density of states.

• Received 17 June 1991

DOI:https://doi.org/10.1103/PhysRevB.44.11536