e-mail:J.Dobson@griffith.edu.au

We point out the non-universality of the asymptotic behavior of dispersion forces, such that the usual sum of inverse sixth power atom-atom contributions R

A technologically important case is the interaction between the pi-conjugated electrons in graphitic structures such as intercalated graphite and nanotube arrays. Starting from the standard tight-binding model of the electron Bloch states in a graphene layer, we evaluate the mutual electronic correlation energy between two layers separated by a large distance D, within the nonlocal electromagnetically non-retarded Random Phase Approximation.

For undoped layers at zero temperature we find that this attractive energy falls off as D

These asymptotic results for "stretched" matter suggest that revisions are required to several currently popular energy functionals for soft layered matter. We also briefly discuss some evidence for the inadequacy of standard theory for layered systems near to their equilibrium spacing.