Free-electron bands graphite

VVe may approximate the n bands in graphite by a two-dimensional free-electron band. The density of states in two-dimensional wave number space is lAjlflnf, where A is the area of llie. system, obtained just as the 2Q.I 2nY for three dimensions. There is one n electron per atom, so you may find the Fermi energy p Just as in three dimensions. This is to be compared with half the a-band width (there are two atoms per primitive cell), which can be read directly from the figure in Problem 3-3. 

During the intercalation of lithium cations between the graphitic carbon layers, the accumulation of positive charge is compensated in part by the intake of electrons into the conducting band of the 7r-bonding system. In most cases the lithium ion electron household is not fully balanced so that a remarkable enhancement of the electronic conductivity follows by quasi-free electrons. The capacity for intake of lithium ions is limited. It was found that lithium ions could be incorporated into... 

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