Uniform tensile elongation in Au-Si core-shell nanowires

In order to evaluate the role of a hard amorphous silicon (a-Si) shell on the deformation of a soft crystalline gold core, we investigated the mechanical properties of the Au@a-Si core-shell nanowire (NW) by using molecular dynamics simulations. We first optimized an existing parametrization of the MEAM potential to better reproduce the mechanical properties of gold and silicon as well as Au-Si interactions. The comparison of the tensile tests performed on pristine Au NW, a-Si shell and Au@a-Si core-shell NW revealed that the hard amorphous shell works against the growth of the ledges left by localized plasticity. In consequence, the localized plasticity and the expansion of nano-twin are reduced. A homogeneous plastic deformation of the core-shell was then observed at almost a constant flow stress equal to the yield stress. This behavior is characteristic of an elastic-perfect plastic material.