Graphite, intercalation compounds electronic properties

Alstrom, P. 1986. Electronic properties of first-stage heavy alkali metal graphite intercalation compounds. Synth. Metals 15 311-322. 

J. E. Fisher, Electronic Properties of Graphite Intercalation Compounds in Physics and Chemistry of Materials with Layered Structures, ed. F. Levy, Reidel, Dordrecht, Holland, 1977, Vol. 5, in the press L. B. Ebert and H. Selig in Abstracts of Franco-American Conference on Intercalation Compounds of Graphite, May 23—27, La Napoule, France. 

Carbon atoms crystallize in several forms. Graphite and diamond are well known carbon polymorphs. Fullerenes, which were discovered in the 1980 s, have also been well characterized. Carbon materials show a variety of different physical and chemical properties. Because of this the electronic structure of carbon materials has been investigated using a number of different experimental techniques, for example, XPS, UPS and XANES. Theoretical studies of carbon materials have been also performed. However, experimentally observed spectra are not always consistent with theoretical predictions. Recently, in order to understand the various kinds of observed electronic spectra, DV-Xa calculations have been performed on a small cluster model. [1] In the present paper, we report results of DV-Xa calculations performed on the carbon materials graphite, alkali graphite intercalation compounds (GIC), fullerene, and fluorinated fullerenes. 

The properties of the intercalation compound, potassium graphite, KCg, have been detailed in several review articles.34/35 The bonding in potassium graphite is described in terms of the limiting structure, K+Cg", and it is believed that the anion forms as a result of the transfer of an electron from the alkali metal to the conduction band of graphite. Novikov and Volpin35 have noted a similarity between aromatic radical-anions and alkali metal-graphite intercalation compounds. Their observation was based on inspection of reduction potentials of aromatic hydrocarbons relative to biphenyl, Table 9.2 ... 

Attempts to elucidate the bonding have concentrated mainly on graphite-FeCla- This intercalate is especially suitable as a model compound, because the magnetic and Mossbauer properties of the iron nucleus constitute excellent probes for electronic structure and environment of the latter. 

As already mentioned the fundamental condition which must be fulfilled for intercalation to occur is electron transfer from the graphite macromolecule to intercalate or vice versa. This quantity determines directly many physiocochemical properties of GICs. For example, it is obvious that for an acceptor compound the quantity of electrons lost by the graphene layers (some other time understood as the hole concentration), must exactly be compensated by the amount of electrons accumulated in the intercalate layers to assure the electrical balance of the intercalation system. The formation of acceptor and donor-type compounds in the reactions of anodic oxidation and cathodic reduction may be represented by the following equations, respectively,... 

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