Diffusive Atomistic Dynamics of Edge Dislocations in Two Dimensions

TL;DR

This paper uses the Phase Field Crystals model to simulate dislocation processes like glide, climb, and annihilation in two-dimensional materials, revealing their dynamics without relying on traditional elasticity theory.

Contribution

It demonstrates that dislocation dynamics can be accurately modeled with a continuum field theory without explicit elasticity or Peierls potential considerations.

Findings

Dislocation glide and climb are reproduced without elasticity theory.

Dislocation mobility can be described by viscous motion equations.

Critical annihilation distance depends on separation angle.

Abstract

The fundamental dislocation processes of glide, climb, and annihilation are studied on diffusive time scales within the framework of a continuum field theory, the Phase Field Crystals (PFC) model. Glide and climb are examined for single edge dislocations subjected to shear and compressive strain, respectively, in a two dimensional hexagonal lattice. It is shown that the natural features of these processes are reproduced without any explicit consideration of elasticity theory or ad hoc construction of microscopic Peierls potentials. Particular attention is paid to the Peierls barrier for dislocation glide/climb and the ensuing dynamic behavior as functions of strain rate, temperature, and dislocation density. It is shown that the dynamics are accurately described by simple viscous motion equations for an overdamped point mass, where the dislocation mobility is the only adjustable parameter. The critical distance for the annihilation of two edge dislocations as a function of separation angle is also presented.