Electronic-structure study of an edge dislocation in Aluminum and the role of macroscopic deformations on its energetics

TL;DR

This study uses orbital-free density functional theory to analyze the core structure and energetics of an edge dislocation in Aluminum, revealing a larger core size than previously thought and the influence of macroscopic deformations on dislocation behavior.

Contribution

It introduces a real-space orbital-free DFT approach to study dislocation cores, showing the significant impact of macroscopic deformations on dislocation energetics and forces.

Findings

Dislocation core size is about ten times the Burgers vector.

Dislocation dissociates into Shockley partials with 12.8 Å separation.

Core-energy depends on macroscopic strain, affecting dislocation dynamics.

Abstract

We employed a real-space formulation of orbital-free density functional theory using finite-element basis to study the defect-core and energetics of an edge dislocation in Aluminum. Our study shows that the core-size of a perfect edge dislocation is around ten times the magnitude of the Burgers vector. This finding is contrary to the widely accepted notion that continuum descriptions of dislocation energetics are accurate beyond 1-3 Burgers vector from the dislocation line. Consistent with prior electronic-structure studies, we find that the perfect edge dislocation dissociates into two Shockley partials with a partial separation distance of 12.8 $\AA$. Interestingly, our study revealed a significant influence of macroscopic deformations on the core-energy of Shockley partials. We show that this dependence of the core-energy on macroscopic deformations results in an additional force on dislocations, beyond the Peach-Koehler force, that is proportional to strain gradients. Further, we demonstrate that this force from core-effects can be significant and can play an important role in governing the dislocation behavior in regions of inhomogeneous deformations.