Defect generation and diffusion mechanisms in Al and Al–Cu

A defect generation mechanism, namely, the grain-boundary Frenkel pair model, and corresponding diffusion mechanisms during electromigration are developed using atomic simulation techniques in Al and Al–Cu. We contend that large numbers of interstitials and vacancies exist at grain boundaries and both contribute to mass transport. Cu preferentially segregates to the interstitial sites at grain boundaries via a Frenkel pair generation process and reduces the overall grain-boundary diffusivity due to the stronger Al–Cu binding. Predictions from our models are in excellent agreement with available experimental data and observations.