First-Principles Study on the Mobility of Screw Dislocations in BCC Iron

TL;DR

This study uses first-principles calculations to map the Peierls barrier of screw dislocations in BCC iron, revealing the migration path and barrier profile, and predicts kink activation energy consistent with experiments.

Contribution

It introduces an efficient correction method for finite size effects in first-principles calculations and clarifies the dislocation migration path in BCC iron.

Findings

Migration path is close to a straight line in the {110} plane.

Peierls barrier profile is single-humped.

Predicted kink activation energy is 0.73 eV, matching experimental data.

Abstract

The fully two-dimensional Peierls barrier map of screw dislocations in BCC iron has been calculated using the first principles method to identify the migration path of a dislocation core. An efficient method to correct the effect of the finite size cell used in the first principles method on the energy of a lattice defect was devised to determine the accurate barrier profile. We find that the migration path is close to a straight line which is confined in a $\{110\}$ plane and the Peierls barrier profile is single-humped. This result clarifies a reason that the existing empirical potentials of BCC iron fail to predict the correct mobility path. A line tension model, incorporating these first principles calculation results, is used to predict the kink activation energy to be 0.73 eV in agreement with experiment.