Defect energies of graphite: Density-functional calculations

The energies of point defects in graphite have been calculated from first principles. The various interplane interstitial configurations are found to have a wider range of energies than in some earlier calculations, implying a larger interstitial migration energy than previously expected (> 1.5 eV). Interplane interstitials are found to be stabilized by a shear of one graphite plane with respect to its neighbors, as this allows the interstitial to bond to three or four atoms in two planes in the ylid and spiro configurations. The minimum interstitial formation energy in sheared graphite is only 5.3 eV compared to 6.3 eV in perfect graphite. Such interstitials form a strongly bound vacancy-interstitial pair with a formation energy of only 10.2 eV. The formation energy of a single vacancy is 7.6 eV. The formation energy and the activation barrier of the Stone-Wales defect in a single layer of graphite were also calculated.