ELECTRONIC-STRUCTURE OF C-78 AND C-78-GRAPHITE COINTERCALATION COMPOUND

We study the electronic structure of C-78 and that of C-78-graphite cointercalation compound. First we show the electronic structure of five isomers of C-78 Their geometric structures have been optimized by an empirical model potential and their electronic structure has been calculated using the tight-binding model. The C-2v-symmetry C-78, a major isomer experimentally extracted, is found to have a considerably deep lowest unoccupied state. Using this C2vC78, we design a stage-1 C-78-graphite cointercalation compound. Its electronic structure calculated with the tight-binding model shows that the deep lowest unoccupied state of the C2v C-78 causes charge transfer from a graphite sheet to C-78. Although the material is formed with only carbon atoms, C-78-graphite cointercalation compound is the hole doped graphite intercalation compound.