Bulletin of ANPA

Abstract submitted to ANPA Conference July 14–16, 2023

Volume 5, Number 1

Condensed Matter Physics and Material Science

Abstract ID: ANPA2023-N00047

Abstract:

ANPA2023-N00047: Atomistic simulation of dislocation nucleation in defect-free copper nanoparticles

Authors:

• Nishchal Thapa Magar; George Mason University

• Raj Kiran Koju; George Mason Univetsity

• Yuri Mishin;

It is well-known that materials become increasingly stronger as their dimensions are reduced to the sub-micrometer scale and even stronger on the nanometer scale. While the “smaller is stronger” paradigm is widely accepted, the exact mechanisms behind the high strength of nanometer-scale objects remain elusive and call for further investigations. In particular, defect-free metallic nanoparticles often demonstrate compressive strength approaching the theoretical strength of the material. The underlying plasticity mechanism in such particles is believed to be related to the nucleation of lattice dislocations on the particle surface. In this work, we applied large-scale molecular dynamics simulations to better understand the onset of plastic deformation in Cu nanoparticles. Single-crystalline nanoparticles with diameters ranging from 17 to 90 nm had smoothed Wulff shapes and were deformed by simulated compression normal to the (111) facets. The particle strength increased with decreasing diameter, reaching about 26 GPa for the smallest size tested. The plastic deformation was initiated by the nucleation of a single dislocation or a group of dislocations on either the top or bottom facet of the particle, usually near a facet corner. Two nucleation mechanisms were identified. In the first mechanism, a Shockley partial half-loop nucleated at the surface after multiple nucleation attempts. After the nucleation of a trailing partial, the full dislocation rapidly traversed the nanoparticle resulting in the nucleation of multiple additional dislocations and a stress drop. In the second mechanism, a partial dislocation loop nucleated under the surface homogeneously and grew on a (111) plane near parallel to a top or bottom facet. The loop eventually reached the particle surface and caused an avalanche of new dislocations and a stress drop. This work has clarified the atomic-scale mechanisms of dislocation-controlled plasticity in nanoscale materials.

To cite this abstract, use the following reference: https://anpaglobal.org/conference/2023/ANPA2023-N00047