# Fermi energy (in graphite)

Gold Member

## Homework Statement

Graphite has a structure of parallel planes weakly interacting with each others such that for many effects it can be considered as two dimensional. Each plane has a hexagonal (honeycomb) structure with a single C atom by site which gives 1 electron of conduction. Assume that the model of free electrons can be applied to all conduction electrons, find the Fermi energy.

## Homework Equations

Not really sure. Are there some missing data?

## The Attempt at a Solution

What boggles me is that there's no volume given nor electron density. I don't think I can calculate the latter either, because even though I know there is 1 atom per elementary unit, I do not know the distance between atoms (not sure it even makes sense in a honeycomb structure). Thus I don't really know how to tackle the problem.
I know that $E_F= \frac{\hbar ^2 \pi n }{m}$. I know that n is the density of electron for an area unit but that number is an unknown in the problem.
I'd like some tip to start the problem, thank you!

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