Diffusion along [001] tilt boundaries in the Au/Ag system-II. atomistic modeling and interpretation

The low temperature boundary diffusion data obtained in Part I were modeledusing elementary vacancy, interstitialcy and interstitial defect mechanisms. First, boundary structures were calculated using the embedded atom method. Point defect formation energies at different boundary sites and migration energies betweenthem were then calculated, and values of δ_bD_b were determined using recently developed expressions for this quantity. The results indicate that the diffusion is dominated by a small number of jumps having relatively small activation energies and large partial correlation factors. Also, interstitial-related mechanisms make important (and perhaps dominant) contributions to the diffusion. Both the data and modelling indicate Arrhenius pre-exponential factors considerably smaller than those reported at high temperatures. It is suggested that additional jumps (possessing higher effective activation energies) exist, and that thei contributions become dominant at high temperatures. Finally, the observed δ_bD_b vs misorientation behavior is found to be quatitatively consistent with the structural unit model.