Geometry-controlled competition between axis centering and detwinning in fivefold-twinned gold nanoparticles

TL;DR

This study uses molecular dynamics to explore how surface curvature and defect depth influence the stability and movement of disclinations in fivefold-twinned gold nanoparticles, revealing geometry-controlled competition between axis centering and detwinning.

Contribution

It uncovers how geometric modifications affect disclination behavior, providing insights for designing stable, defect-engineered nanomaterials.

Findings

Concave geometries promote surface diffusion restoring fivefold symmetry.

Convex structures with shallow axes undergo rapid detwinning within nanoseconds.

Positioning the axis two atomic layers beneath the surface suppresses detwinning.

Abstract

Fivefold-twinned metal nanoparticles host a central wedge disclination that strongly influences their mechanical and catalytic properties. Yet the atomistic mechanisms governing the stability, migration, and annihilation of this topological defect remain incompletely understood. Here we present a systematic molecular dynamics study of gold Marks decahedra in which the fivefold axis is artificially brought close to the surface by controlled geometric modifications. By generating concave and convex morphologies with varying axis depth, we uncover a geometry-controlled competition between axis centering and detwinning. Concave geometries promote surface diffusion that restores fivefold symmetry, either by recentering the original disclination or by nucleating a new subsurface axis through collective atomic rearrangements. In contrast, convex structures with a shallow axis undergo rapid detwinning within the first nanoseconds via surface glide, leading to single-twin or fully FCC configurations. Remarkably, positioning the axis just two atomic layers beneath the surface suppresses detwinning and restores stability. Our results demonstrate that surface curvature and defect depth critically regulate disclination mobility and twin stability, providing a mechanistic framework to understand the structural evolution of multi-twinned nanoparticles and to guide the controlled design of defect-engineered nanomaterials.