Energetics of Defects and Diffusion Mechanisms in Graphite

Abstract

Extensive first-principles calculations are presented for the formation energies and migration barriers of elementary defects in graphite, as well as for the activation energy of atomic exchange. The calculations show that the long-held view, that atomic diffusion in graphite occurs via the direct-exchange mechanism, is incorrect, although more complicated exchange processes have not been ruled out. We find that diffusion in graphite is most likely mediated by vacancies with an activation energy which is lower than that of the interstitial and the direct-exchange mechanisms, and is in reasonable agreement with experiment.