Graphitizationat diamond dislocation cores

Abstract

We examine possible mechanisms for graphitization at dislocation coresin diamond, both as an explanation for brown coloration in naturalbrown diamond and as a model for annealing in amorphous carbonmaterials. We find a metastable structure for the 90° partialdislocation core where bonds are broken in both single- and double-period structures leading to a row of paired sp2 C atoms. Weexamine the effect of hydrogen and other impurities on this corestructure both through direct interaction and potential chargingeffects. We also investigate a mechanism for progressivearomatization through the migration and aggregation of 30°partial dislocations.