Effect of Cu and Ag solute segregation on βsn grain boundary diffusivity

We investigate the effect of various amounts of Ag and Cu solute atoms on the self-diffusivity of Sn in the (101) symmetric tilt βSn grain boundary. Using molecular dynamics simulations over a temperature range of 300 K to 450 K, we show that both Ag and Cu decrease the grain boundary self-diffusivity of Sn as the amount of solute in the interface increases. Additionally, the presence of Ag at the grain boundary interface causes a greater reduction in the self-diffusivity of Sn when compared to Cu. We also analyze the solute effect on the diffusive width of the interface and find that low concentrations of both Ag and Cu shrink the width relative to the pure Sn interface. However, adding Cu in excess density greater than 5 × 10^-3 atoms/Å ² causes the interface to expand to values almost twice the original width, possibly caused by the larger cohesive energy of Cu-Sn versus Sn-Sn.