Glissile dislocations with transient cores in silicon

TL;DR

This study reveals that in silicon, the only mobile dislocation cores are unstable and stress-driven, challenging previous assumptions and impacting understanding of dislocation motion during deformation.

Contribution

It demonstrates that all stable dislocation cores in silicon are sessile, and the mobile core is an unstable configuration, a novel insight from first-principles calculations.

Findings

Stable cores are sessile in silicon dislocations.

The only glissile core is unstable and stress-driven.

Implications for interpreting dislocation observations.

Abstract

We report an unexpected characteristic of dislocation cores in silicon. Using first-principles calculations, we show that all the stable core configurations for a non-dissociated 60$^\circ$ dislocation are sessile. The only glissile configuration, previously obtained by nucleation from surfaces, surprinsingly corresponds to an unstable core. As a result, the 60$^\circ$ dislocation motion is solely driven by stress, with no thermal activation. We predict that this original feature could be relevant in situations for which large stresses occur, such as mechanical deformation at room temperature. Our work also suggests that post-mortem observations of stable dislocations could be misleading, and that mobile unstable dislocation cores should be taken into account in theoretical investigations.