Peierls-Nabarro Modeling of Dislocations in High Entropy Alloys

Dislocations in alloys with random solute distributions, short-range order, or clustering have a range of competing length and energy scales that establish overall energy barriers to dislocation motion. The flow stress then depends on many different underlying atomistic material parameters and emergent length scales. To gain understanding and to guide theory development, we show how an extended Peierls-Nabarro (PN) model can enable highly efficient scale bridging along with parametric exploration of dislocation behavior as a function of material parameters. However, local fluctuations in the atomic forces acting on the dislocation cannot be measured using the atom-level virial stress. Studies then show that variations in the unstable fault energy have negligible effects on strength compared to stress fluctuations due to solute misfits, consistent with misfit-based theory. Comparisons of the extended PN model predictions to direct atomistic nudged-elastic band simulations of the dislocation energy landscape in a model bcc HEA show the fidelity/accuracy of the extended PN model and role of core structure. The PN model is then applied to study the configurations, energies, and motion of long, intrinsically wavy, dislocations with comparisons to analytic theory.