Screw dislocation in zirconium: An ab initio study

TL;DR

This study uses ab initio density functional theory to analyze the core structure and glide behavior of screw dislocations in zirconium, revealing dissociation in the prism plane and a low Peierls barrier consistent with experimental observations.

Contribution

It provides detailed atomic-scale insights into zirconium screw dislocations and evaluates the accuracy of empirical potentials against ab initio results.

Findings

Dislocations dissociate in the prism plane into partials with screw character.

Basal plane dissociation is unstable for zirconium dislocations.

Peierls barrier is small, with a stress below 21 MPa, matching experiments.

Abstract

Plasticity in zirconium is controlled by 1/3<1-210> screw dislocations gliding in the prism planes of the hexagonal close-packed structure. This prismatic and not basal glide is observed for a given set of transition metals like zirconium and is known to be related to the number of valence electrons in the d band. We use ab initio calculations based on the density functional theory to study the core structure of screw dislocations in zirconium. Dislocations are found to dissociate in the prism plane in two partial dislocations, each with a pure screw character. Ab initio calculations also show that the dissociation in the basal plane is unstable. We calculate then the Peierls barrier for a screw dislocation gliding in the prism plane and obtain a small barrier. The Peierls stress deduced from this barrier is lower than 21 MPa, which is in agreement with experimental data. The ability of an empirical potential relying on the embedded atom method (EAM) to model dislocations in zirconium is also tested against these ab initio calculations.