Atomistic Understanding of the Competition between Dislocation and Twinning in Silver under Nanoindentation

In this study, the competition mechanisms between dislocation slip and twinning in silver with a low stacking fault energy using molecular dynamics (MD) simulation from an atomistic point of view are reported. Herein, three crystallographic surface orientations of (001)$\left(\right. 001 \left.\right)$, (011)$\left(\right. 011 \left.\right)$, and (111)$\left(\right. 111 \left.\right)$ are considered and compared. The indentation stress-strain curves are successfully obtained from the load-displacement curves of nanoindentation. The stress of (001)$\left(\right. 001 \left.\right)$, (011)$\left(\right. 011 \left.\right)$, and (111)$\left(\right. 111 \left.\right)$ orientations drops at the strains of 0.140, 0.133, and 0.136, which corresponds to the yield stress of 3.83, 4.33, and 4.99 GPa, respectively. Dislocation slip and twinning simultaneously form in silver as indicated by the total potential energy of the system. Furthermore, the typical four-, two-, and sixfold symmetries of the out-of-plane displacement as in copper are not observed for (001)$\left(\right. 001 \left.\right)$, (011)$\left(\right. 011 \left.\right)$, and (111)$\left(\right. 111 \left.\right)$ orientations in silver. Hence, this observation can be supported by the simultaneous occurrence of dislocation slip and twinning in silver.

Automated summary

In this study, the competition mechanisms between dislocation slip and twinning in silver with a low stacking fault energy were investigated using molecular dynamics simulation. Three crystallographic surface orientations were considered and compared. The yield stress and the occurrence of dislocation slip and twinning were analyzed. The results indicate that simultaneous dislocation slip and twinning occur in silver.