Graphene K and K' States at the Dirac Point

The graphene band structure states at the K and K' points and the Fermi level, the Dirac point, computed when a (1x1) unit cell is employed, fall at the gamma point when a (3x3) unit cell is employed. These states at the gamma point of the Brillouin zone for the (3x3) unit cell have a zero phase factor and are conveniently represented as molecular orbitals of pi electrons. These states are illustrated and discussed.