Length and Twin Thickness–Dependent Mechanical Properties in Twinned Silicon Nanowires: A Molecular Dynamics Study

This study employs molecular dynamics simulations under tensile loads to thoroughly examine how variations in nanowire lengths and twin thicknesses affects the various mechanical properties; such as yield strength and deformation behaviors; like failure modes with cylindrical cross-sectioned silicon nanowires. It investigates the effects of nanowire length and twin thickness variations with the alignment of Σ3 CTBs along <001˃ axis. Analysis of nanowire models with lengths ranging from 70 to 100 nm and twin thicknesses between 2 and 10 nm reveals that longer nanowires exhibit superior mechanical performance while reduced twin thickness enhances both strength and ductility. Compared to single-crystal counterparts; longer twinned silicon nanowires consistently demonstrate significant mechanical improvements outperforming shorter ones. These variations also affect brittle-to-ductile and ductile-to-brittle transitions among other failure modes. Plastic deformation analysis indicates that both partial and full dislocation emissions from free surfaces affect the yield stress. Additionally; accumulation, propagation, and glide of dislocations near CTBs improved the yield stress and facilitated the ductile-to-brittle transition. This research provides valuable insights into how twin thickness and nanowire length affect the various mechanical properties of non-metallic materials and systems.