Using density-functional-theory methods with an exchange and correlation functional which takes into account the interlayer van der Waals interaction in systems without any material-specific empirical parameters, a study was made of the energetics and migration of single- and di-interstitials in graphite and bilayer graphene. It was shown that two classes of interstitials, so-called bound and free, could co-exist. The latter were mobile at room and lower temperatures, which explains the experimental data and reconciles them with the results of atomistic simulations. The results shed light on the behavior of graphite and carbon nanotubes under irradiation and had implications for the irradiation-mediated processing of bilayer graphene.

Bound and Free Self-Interstitial Defects in Graphite and Bilayer Graphene: a Computational Study. A.Gulans, A.V.Krasheninnikov, M.J.Puska, R.M.Nieminen: Physical Review B, 2011, 84[2], 024114