Stress-dependent Peierls potential: Influence on kink-pair activation

Atomistic calculations based on the nudged elastic band method for a Lomer dislocation in aluminum evidence a dependence of the Peierls potential on the applied shear stress in such a way that the Peierls stress predicted from the zero-stress potential is half its true value for the case considered here. Stress-dependent Peierls potentials that are extracted are then introduced as substrate potentials in a string model with a line tension (LT) adjusted to match the dislocation kink width obtained from atomistic simulations. The LT model is found to predict accurately dislocation saddle configurations and corresponding kink-pair activation enthalpies for a wide range of stresses. In particular, it is shown that the stress dependence of the Peierls potential is required to model with accuracy the nonlinearity of the enthalpy-stress curve.