Molecular dynamics study of mechanical behavior of gold-silicon core-shell nanowires under cyclic loading

Abstract

Composite systems at nanoscale are promising to design new materials combining different interesting properties, like high strength and good plasticity. In the present work, we compare mechanical properties of gold-silicon core-shell and pure gold nanowires subjected to several tensile loadings and compressive unloadings at 300 K and 1 K, in order to evaluate the ability of a hard amorphous silicon shell to stabilize a crystalline gold core during cyclic loading. The hard shell appears involved in the quasi-reversible macroscopic plasticity of core-shell NW, by promoting twins, stacking fault and isolated full dislocations, due to a confinement effect of the core. In addition, our simulations revealed that the reversible behavior is progressively lost over cycles. The analysis of the amorphous shell shows that large strains combined with high strain rate prevent self-healing of the shell, leading to shell failure and to reversibility loss.