Ab Initio Study of Screw Dislocations in Mo and Ta: A new picture of plasticity in bcc transition metals

TL;DR

This study uses ab initio density-functional calculations to reveal a new, more symmetric core structure of screw dislocations in Mo and Ta, challenging previous models and aligning better with experimental data on dislocation mobility.

Contribution

It provides the first ab initio analysis of screw dislocation cores in Mo and Ta, proposing a new symmetric core structure that revises existing models of bcc plasticity.

Findings

Dislocation cores are symmetric and compact.

Core energy scales match experimental Peierls barriers.

Revises the traditional picture of bcc dislocation cores.

Abstract

We report the first ab initio density-functional study of <111> screw dislocations cores in the bcc transition metals Mo and Ta. Our results suggest a new picture of bcc plasticity with symmetric and compact dislocation cores, contrary to the presently accepted picture based on continuum and interatomic potentials. Core energy scales in this new picture are in much better agreement with the Peierls energy barriers to dislocation motion suggested by experiments.