Simulation of plasticity in nanocrystalline silicon

Abstract

Molecular dynamics investigation of plasticity in a model nanocrystalline silicon system demonstrates that inelastic deformation localizes in intergranular regions. The carriers of plasticity in these regions are atomic environments, which can be described as high-density liquid-like amorphous silicon. During fully developed flow, plasticity is confined to system-spanning intergranular zones of easy flow. As an active flow zone rotates out of the plane of maximum resolved shear stress during deformation to large strain, new zones of easy flow are formed. Compatibility of the microstructure is accommodated by processes such as grain rotation and formation of new grains. Nano-scale voids or cracks may form if stress concentrations emerge which cannot be relaxed by a mechanism that simultaneously preserves microstructural compatibility.

Acknowledgements

We would like to thank D. Wolf, P. Keblinski and V. Yamakov for making their MD codes available to us. We are also grateful to S. Veprek, M. Bazant, S. Yip, C. Ashe and D. Danielson for useful discussions. The atomic structure visualizations presented here were generated using the AtomEye program 45. This manuscript is based upon work supported by the NSF Graduate Fellowship, the Los Alamos National Laboratory Director's Postdoctoral Fellowship and the Defense University Research Initiative on NanoTechnology (DURINT) on ‘Damage-and Failure-Resistant Nanostructured and Interfacial Materials’, funded at the Massachusetts Institute of Technology by the Office of Naval Research under grant N00014-01-1-0808.