Cohesive Energy Studies of Intercalated Graphite Compounds: The Madelung Energies of C₆Li and C₈K

The Madelung energies EM of the lamellar intercalated compounds C6Li and C8K are -4.571 eV/atom of Li and -2.478 eV/atom of K respectively, assuming full charge transfer. EM becomes more negative when the counterion coordination becomes greater, and depends critically on Coulomb contributions in directions normal to the graphite planes. Born-Haber cycle estimates of the enthalpy of formation of C8K (-0.93 eV to -1.79 eV, depending on which band theory estimate of the Fermi energy shift is used) bracket the experimental value of -1.208 eV.