The strength of true metallic nanowires and nanopillars (diameters below 100 nm) is known to be higher than the strength of bulk metals and is most likely controlled by dislocation nucleation from free surfaces. Dislocation nucleation is a thermally activated process that is sensitive to both temperature and strain rate. However, most simulations rely on high strain rate molecular dynamics to investigate strength and nucleation, which is limited by short molecular dynamics time scales. In this work, the energetics of dislocation nucleation in gold nanowires are computed using atomistic simulations, and transition state theory is used to estimate the strength at experimental strain rates revealing detailed information outside the realm accessible to molecular dynamics simulations. This allows investigation into the competition between thermally activated dislocation nucleation and other failure mechanisms such as elastic and structural instabilities. Additionally, the mechanisms of dislocation nucleation are compared against analytical continuum models which allow a better understanding of the nucleation process including the effects of the wire surfaces. This study helps clarify and consolidate our understanding of the nature of dislocation nucleation in small structures.
Bibliographical noteFunding Information:
The authors wish to acknowledge useful discussions with Dr. Jonathan Zimmerman and Prof. Wei Cai. This research was supported in part by an appointment to the Sandia National Laboratories Truman Fellowship in National Security Science and Engineering, sponsored by Sandia Corporation (a wholly owned subsidiary of Lockheed Martin Corporation) as Operator of Sandia National Laboratories under its U.S. Department of Energy Contract no. DE-AC04-94AL85000 . A.T.J. and J.R.G. gratefully acknowledge the financial support of the National Science Foundation through ATJ's NSF Graduate Research Fellowship and JRG's CAREER grant ( DMR-0748267 ). K.K. acknowledges support from Los Alamos National Laboratories through LDRD-DR.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering