Structures and recombination routes were deduced for interstitial-vacancy (I-V) pairs in graphite. Interaction resulted in the formation of a new metastable defect (an intimate I-V pair) or a Stone-Wales defect. The intimate I-V pair, although 2.9eV more stable than its isolated constituents, still required a formation energy of 10.8eV. The barrier to recombination to give perfect graphite was calculated to be 1.3eV. This was consistent with the experimental first Wigner energy release peak at 1.38eV. Similar defects were expected to form in C nanostructures such as nanotubes, nested fullerenes and onions under irradiation.

Metastable Frenkel Pair Defect in Graphite - Source of Wigner Energy? C.P.Ewels, R.H.Telling, A.A.El-Barbary, M.I.Heggie, P.R.Briddon: Physical Review Letters, 2003, 91[2], 025505 (3pp)