Interstitials in graphite and disordered carbons

The steps in the interlayer spacing observed in annealing studies of artificial carbons on the one hand, and those seen in fast-neutron irradiation and grinding of graphite on the other hand, are shown to demonstrate the existence of interstitial carbon atoms between the aromatic planes of carbon atoms, $s{p}^2$ bonded as in the graphite-crystal structure. The steps are analogous to staging in graphite intercalation compounds.