Views of the graphene sheet. Left: side view of the (4√3 × 4√3) graphene cell with a height of 30 Å. Right: scheme of the different cells considered in this work: the green solid line represents the (2 × 2) unit cell; the green dotted line the (4 × 4) unit cell; the red solid line the (√3 × √3) cell, which is rotated 30° from the unit cell; the red short-dotted line the (2√3 × 2√3) cell; and the long-dotted line the (4√3 × 4√3) cell.