Shockley partial dislocations to twin: Another formation mechanism and generic driving force

We report a mechanism of twin formation from two Shockley partial dislocations on non-neighboring glide planes. Further, we correlate the driving force of twin nucleation with the local stress of large magnitude. Using the embedded atom method potential for atomic interactions, our molecular dynamics simulations of Cu nanograins and a single crystal reveal the formation mechanism and identify the driving force. Stacking faults expand under high stress, increasing their energy and making their transformation to a twin energetically favorable. Although this study focuses on only Shockley partial dislocations on non-neighboring glide planes, the driving force—the stress of large magnitude—is expected to apply also to the twin formation from Shockley partial dislocations on neighboring glide planes.