Two types of methods are commonly used to describe the van der Waals cohesive properties of graphitic systems: one is based on density functional theory and the other on empirical model potentials. This paper examines the relation between the two and finds that, when properly done, both methods give the same results. The local density approximation (LDA) method can describe cohesion when graphitic molecules are close together, but must be supplemented with the theory of dispersion forces when the intermolecular distance increases. It is found that LDA dispersion force calculations reproduce the empirical potentials, which are thereby validated by fundamental theory. A recent disparity between two types of calculations in determining binding energy of ${\mathrm{C}}_{60}$ molecules inside a (10,10) nanotube is also examined.

• Received 25 September 2001

DOI:https://doi.org/10.1103/PhysRevB.65.125404