Diana Nelli | Searcharxiv

arXiv2026

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

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.

cond-mat.mes-hall↗

arXiv2025

General theory for packing icosahedral shells into multi-component aggregates

Multi-component aggregates are being intensively researched in various fields because of their highly tunable properties and wide applications. Due to the complex configurational space of these systems, research would greatly benefit from a general theoretical framework for the prediction of stable structures, which, however, is largely incomplete at present. Here we propose a general theory for the construction of multi-component icosahedral structures by assembling concentric shells of different chiral and achiral types, consisting of particles of different sizes. By mapping shell sequences into paths in the hexagonal lattice, we establish simple and general rules for designing a wide variety of magic icosahedral structures, and we evaluate the optimal size-mismatch between particles in the different shells. The predictions of our design strategy are confirmed by molecular dynamics simulations and density functional theory calculations for several multi-component atomic clusters and nanoparticles.

physics.atm-clus↗