Molecular dynamics modeling of self-diffusion along a triple junction

We propose a computational procedure for creating a stable equilibrium triple junction (TJ) with controlled grain misorientations. We apply this procedure to construct a TJ between a Σ5(210) grain boundary (GB) and two general high-angle GBs in copper and calculate the diffusion coefficients along the TJ and the GBs using molecular dynamics with an embedded-atom potential. The TJ diffusion is only a factor of 2 faster than diffusion in the Σ5 GB but significantly faster than diffusion in the general GBs. Both the GBs and the TJ studied here show a premelting behavior near the bulk melting point, where their diffusivities converge to the diffusivity of bulk liquid. Although our results are consistent with the common assumption that TJ diffusion is generally faster than GB diffusion, the difference between the two diffusivities does not appear to be large enough to ensure a significant contribution of TJs to diffusional creep in polycrystals at high temperatures.