Elastic interactions of defects on (111) Au surfaces

We report on the results of molecular-dynamic simulations of vacancy and vacancy-step interactions on a (111) Au surface. Near the vacancy the strain field decays as r-n with n2 and the dilatational strain undergoes a rapid oscillatory decay to zero at a distance of 1 nm from the vacancy. This result suggests that there is no direct long-range elastic interaction between vacancies on this surface. The elastic interaction between a vacancy and a step only becomes significant at separations of less than 1 nm and is controlled by a mixing of the oscillatory pressure field of the step with the dilatational field of the vacancy. Our calculations indicate that a vacancy on the upper portion of a terrace associated with a step has to overcome an energy barrier of 0.1 eV in order for vacancy annihilation to occur at the step edge.