CHARGE-DENSITY AND CHARGE-TRANSFER IN STAGE-1 ALKALI-GRAPHITE INTERCALATION COMPOUNDS

First-principles electronic structure calculations are carried out for the stage-1 alkali graphite intercalation compounds LiC6 and XC(8) (X = Li, Na, K, Rb, and Cs). We analyze the charge densities and the dif ferences to the reference charge densities of graphite host and interc alant sublattice. For the alkali metals Na, K, Rb, and Cs the computed charge transfer is nearly constant at a value of 0.7 elementary charg es (e); values of 0.5e and 0.4e are found for the Li compounds LiC6 an d LiC8, respectively. It is shown that the main fraction, about 0.4e, of the charge transfer is a geometrical consequence of the simple over lap of the charge densities of the graphite and intercalant sublattice s.