Interaction between two graphene sheets with a turbostratic orientational relationship

The interaction of two rigid defect-free graphene sheets with various turbostratic orientational relationships is examined using a Lennard-Jones potential. When one layer is rotated from the AB stacking order, maxima and minima in the potential energy occur at angles corresponding to AA and AB stacking. The energy gap between AA and AB stacking is estimated to be much smaller than the average thermal energy at room temperature. Turbostratic orientations diminish the energy for translational displacement to zero. The presence of defects is required to explain non-zero shear strengths in pure carbon nanotube fibres with no commensurate orientation of graphene sheets.