Supersonic Dislocation Kinetics from an Augmented Peierls Model

Area of Science:

• Solid-state physics
• Materials science
• Mechanics of materials

Background:

• The speed limit for dislocation motion is a long-standing debate in materials science.
• Previous models did not fully capture the complex dynamics of dislocations.
• Recent atomistic simulations suggest dislocations may exceed wave speeds.

Purpose of the Study:

• To investigate whether dislocations can propagate faster than shear or longitudinal waves.
• To develop a theoretical model predicting dislocation speeds under applied stress.
• To reconcile theoretical predictions with experimental and simulation data.

Main Methods:

• Utilized the Peierls model, incorporating drag and gradient effects.
• Derived a kinetic relation between applied shear stress and dislocation velocity.
• Analyzed the model for regimes of stable and unstable dislocation motion.

Main Results:

• The modified Peierls model predicts intersonic and supersonic dislocation speeds at high applied stress.
• Identified specific regimes where dislocation motion becomes unstable.
• Theoretical predictions align with findings from recent atomistic simulations.

Conclusions:

• Dislocations are capable of exceeding the speed of shear and longitudinal waves.
• The Peierls model, with modifications, accurately describes high-speed dislocation dynamics.
• The study validates the possibility of supersonic dislocation motion and associated instabilities.