Abstract
A computer simulation study of vacancy and interstitial migration along the core of an a/2 〈110〉 {110} edge dislocation has been carried out for MgO with the objective of determining the pipe-diffusion mechanism. Point-ion as well as shell-model potentials have been used. Different diffusion paths have been investigated for vacancies and interstitials along the core of the dislocation. Self-interstitials have been found to exist in very stable configurations, for which the binding energy is about four times greater than for positions of vacancies with the highest binding energies. Computations show that the migration energy is lowered for some vacancy jumps along the core whereas the migration energy for interstitials is increased substantially with respect to the bulk. These atomistic simulations show that pipe self-diffusion very likely proceeds by a vacancy mechanism with an activation energy which is about 70–75% of the calculated value for the bulk. This reduction in activation energy is due mainly to a decrease in the vacancy formation energy for some positions inside the dislocation core, rather than to a substantial reduction in the migration energy in this highly disturbed region.