Towards a universal size-dependent strength of face-centered cubic nanoparticles

Understanding dislocation nucleation is key to controlling the plasticity of a defect-free specimen. Here, we perform an atomistic study of the strength of various Face-Centered Cubic (FCC) defect-free nanoparticles. Compression simulations are performed on Wulff shaped nanoparticles composed of various FCC metals along the [111] crystallographic direction. We show here that all nanoparticles yield by nucleating Shockley partial dislocations at the vertices. The compressive stress at which the partial dislocations nucleate is smaller for larger particles for all of the FCC metals studied. The dependence of the strength on the size obeys a power-law, with a universal exponent for all of the FCC nanoparticles. The pre-factor of the powerlaw relationship depends on the material properties. Based on a dimensional analysis and the classical nucleation theory of dislocations, we propose that the exponent corresponds to the geometry, which is similar in all of the FCC metals, and that the pre-factor linearly increases with a dimensionless parameter, which contains different material properties. Based on these results, we discuss a universal law for the strength of FCC nanoparticles and its fundamental difference from the universal law found experimentally for FCC pillars. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.