Entropically Stabilized Dislocations

Abstract

Dislocations are line defects that play a key role in the plasticity of crystalline materials and affect their thermal, chemical, and electrical properties. Typically dislocations are treated as stable defects; e.g., the equilibrium core structure of a dislocation is obtained by minimizing the crystal potential energy with respect to atom positions. Here we show for the first time the possibility of "entropically stabilized dislocations" that exist due to entropic effects without a corresponding potential energy well. An entropically stabilized dislocation was discovered in an accelerated multiscale quasicontinuum simulation. Its entropic nature was verified with fully atomistic free energy calculations and explained by a simple continuum-based model. This result has important consequences for the study of dislocations as well as for temporal multiscale methods that use information from the potential energy surface to accelerate time in molecular simulations.