Wedge disclination description of emergent core-shifted grain boundaries at free surfaces

TL;DR

This paper investigates the atomic and elastic mechanisms behind emergent grain boundaries at free surfaces, demonstrating how core shifts and wedge disclinations influence boundary structures in copper and similar materials.

Contribution

It introduces a combined atomic and elastic analysis that explains the core shift phenomenon and resolves previous discrepancies between computational models and experimental observations.

Findings

Confirmed core shift of boundaries through atomic calculations.

Reconciled atomic and elastic models by including wedge disclinations.

Provided insights into boundary restructuring mechanisms at free surfaces.

Abstract

Emergent grain boundaries at free surface control material properties such as nanomaterial strength, catalysis, and corrosion. Recently the restructuring of emergent boundaries on copper (111) surfaces was discovered experimentally and atomic calculations point to its universality in fcc metal systems. Restructuring is due to a preference for boundaries to shift their tilt axis across the (1-10) plane towards [112] and ultimately to form low energy [112] core shifted boundaries (CSBs). However, the observed geometry of these emergent boundaries is not reproduced by atomic calculations and the driving force is still controversial due to inconsistencies between the computational continuum analysis and atomic calculations. Here, using atomic calculations that involve a methodical shift of the dislocation core, we confirmed the core shift of emergent boundaries observed in experiment and reconciled the atomic calculations with the elastic analysis through the inclusion of a straight wedge disclination at the free surface.