Possible mechanisms of graphitization at dislocation cores in diamond were examined as an explanation for the brown coloration of natural brown diamonds and as a model for the annealing of amorphous C materials. A metastable structure for the 90° partial dislocation core was found, where bonds were broken in both single- and double-period structures so as to lead to a row of paired sp2 C atoms. The effect of H and other impurities upon this core structure was examined via both direct interaction and potential charging effects. A mechanism of progressive aromatization via the migration and aggregation of 30° partial dislocations was also investigated.

Graphitization at Diamond Dislocation Cores. C.P.Ewels, N.T.Wilson, M.I.Heggie, R.Jones, P.R.Briddon: Journal of Physics - Condensed Matter, 2001, 13[40], 8965-72