Statistical mechanics of kinks on a gliding screw dislocation

TL;DR

This paper develops a statistical mechanics model to describe the velocity of screw dislocation glide in bcc metals, revealing a temperature-induced phase transition that affects activation energy and mobility.

Contribution

It introduces an analytical expression for dislocation velocity that captures a phase transition in activation energy, validated by kinetic Monte Carlo simulations.

Findings

Identification of a critical temperature where activation energy halves

Quantitative agreement between analytical model and simulations

Discovery of a phase transition in dislocation mobility

Abstract

The ability of a body-centered cubic metal to deform plastically is limited by the thermally activated glide motion of screw dislocations, which are line defects with a mobility exhibiting complex dependence on temperature, stress, and dislocation segment length. We derive an analytical expression for the velocity of dislocation glide, based on a statistical mechanics argument, and identify an apparent phase transition marked by a critical temperature above which the activation energy for glide effectively halves, changing from the formation energy of a double kink to that of a single kink. The analysis is in quantitative agreement with direct kinetic Monte Carlo simulations.