Modeling dislocation nucleation strengths in pristine metallic nanowires under experimental conditions

The nature of dislocation sources in small-scale metals is critical to understanding and building models of size-dependent crystalline strength at the nanoscale. Pre-existing dislocations with one pinning point can be readily described as truncated Frank–Read sources, and modeling their operation strengths is straightforward. In contrast, simple and accurate models describing surface dislocation nucleation processes remain elusive. Here, we develop a computationally simple model of heterogeneous dislocation nucleation from free surfaces by combining a continuum description of the nucleation process with the atomistic inputs where accuracy is critical. This model is used to derive the upper strength limits of single-crystalline face-centered cubic nanopillars as a function of size, material and crystal orientation for uniaxial compression and tension. The output parameter space of this model is critically compared against direct atomistic simulations, as well as experiments on tension of pristine gold nanowires and compression of copper nanopillars to highlight its virtues and limitations.