SOLID-STATE ELECTRONIC-STRUCTURE OF POTASSIUM GRAPHITE-INTERCALATION COMPOUNDS - THE SYSTEMS KC24 AND KC8

The solid state electronic structures of the potassium graphite interc alation compounds (GIG) KC24 and KC8 are investigated by a crystal orb ital (GO) approach of the intermediate neglect of differential overlap (INDO) type. KC24 crystallizes in a hexagonal and KC8 in an orthorhom bic lattice. The CO results derived for the potassium GIC are compared with CO results of pristine graphite and potassium-doped C-60 fulleri des. An incomplete It-to-graphite charge transfer (CT) of about 50% is predicted for both GIC studied. This incomplete CT in GIC is correlat ed with the incomplete CT ill potassium-doped fullerides predicted in a recent study. The present results call be considered as all a poster iori corroboration of our findings in the case of alkali-doped fulleri des. The acceptor capability of graphite is smaller than the one of ti le C-60 soccerball with its pentagon defects. Modifications ill the el ectronic density of states (DOS) distribution in the potassium GIC rel ative to pristine graphite are analyzed. Tile influence of the excess electrons oil tile graphite electronic structure is described by a par ameter which measures the ''number of covalent bonds'' per CC contact.