Registry-dependent interlayer potential for graphitic systems

Standard applications of density functional theory do not adequately describe the exfoliation energy of graphite. In fact, the local density approximation (LDA) and generalized gradient approximation (GGA) are in qualitative disagreement: the LDA binds at the experimental lattice constant, whereas the GGA does not. However, the variation in the energy under interlayer shifts, due predominantly to the overlap of pi orbitals (not dispersion interactions), is nearly identical in these approximations. We combine these results with experimental information on the exfoliation energy to create an improved registry-dependent classical potential for the interlayer interaction in graphitic structures.