CHARGE-TRANSFER IN RB-INTERCALATED GRAPHITES

Charge transfer in stage-1 and stage-2 Rb graphite intercalation compounds was analyzed in terms of total electron-density distributions. The net charge transfer was decomposed into geometrical and ''physical'' components, obtained by the integration of reference and difference charge densities [n(ref)(r) and deltan(r) = n(r) - n(ref)(r)] respectively over regions associated with the host or the intercalant. The reference charge density is the superposition of charge densities for the host and intercalant sublattices treated separately, and the host-intercalant partitioning is defined by the condition that the normal component of the density gradient vanish at the interface. Employing self-consistent local-density-functional-theory calculations based on separable pseudopotentials and a plane-wave basis, we obtained a physical charge transfer of 0.2 (0.35)e and a geometrical charge transfer of 0.55e, which yield a net charge transfer of 0.75 (0.90)e for stage 1 (2).