Solid state electronic structure of potassium graphite intercalation compounds; the systems KC24 and KC8

Abstract

AbstractThe solid state electronic structures of the potassium graphite intercalation compounds (GIC) KC24 and KC8 are investigated by acrystal orbital (CO) approach of the intermediate neglect of differential overlap (INDO) type. KC24 crystallizes in a hexagonal and KC8 in an orthorhombic lattice. The CO results derived for the potassium GIC are compared with CO results of pristine graphite and potassium‐doped C60 fullerides. An incomplete K‐to‐graphite charge transfer (CT) of about 50% is predicted for both GIC studied. This incomplete CT in GIC is correlated with the incomplete CT in potassium‐doped fullerides predicted in a recent study. The present results can be considered as an a posteriori corroboration of our findings in the case of alkali‐doped fullerides. The acceptor capability of graphite is smaller than the one of the C60 soccerball with its pentagon defects. Modifications in the electronic density of states (DOS) distribution in the potassium GIC relative to pristine graphite are analyzed. The influence of theexcess electrons on the graphite electronic structure is described by a parameter which measures the ‘number of covalent bonds’ per CC contact.