Semiempirical approach to the energetics of interlayer binding in graphite

The interlayer binding energy of graphite is obtained by a semiempirical method in which ab initio calculations based on the density functional theory (DFT) are supplemented with an empirical van der Waals (vdW) interaction. The local density approximation (LDA) and generalized gradient approximation (GGA) are used in the DFT calculations, and the damping (or interpolation) function used to combine these DFT results with an empirical vdW interaction is fitted to the observed interlayer spacing and c-axis elastic constant. The interlayer binding energies calculated in the LDA and GGA are quite different, but the combined results are nearly the same, which may be a necessary condition and provide reinforcements for validating the method. The present results are also consistent with those obtained by the empirical method based on the Lennard-Jones potential, and both are in reasonable agreement with the recent experimental data. These results indicate that, in contrast to the prevailing belief, the LDA underestimates the interlayer binding energy of graphite.