13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Torsional properties of bamboo-like structured Cu nanowires Haifei Zhan and Yuantong Gu* School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD, 4001, Australia * Corresponding author: yuantong.gu@qut.edu.au Abstract Recently, researchers reported that nanowires (NWs) are often polycrystalline, which contain grain or twin boundaries that transect the whole NW normal to its axial direction into a bamboo like structure. In this work, large-scale molecular dynamics simulation is employed to investigate the torsional behaviours of bamboo-like structured Cu NWs. The existence of grain boundaries is found to induce a considerably large reduction to the critical angle, and the more of grain boundaries the less reduction appears, whereas, the presence of twin boundaries only results in a relatively smaller reduction to the critical angle. The introduction of grain boundaries reduces the torsional rigidity of the NW, whereas, the twin boundaries exert insignificant influence to the torsional rigidity. NWs with grain boundaries are inclined to produce a local HCP structure during loading, and the plastic deformation is usually evenly distributed along the axial axis of the NW. The plastic deformation of both perfect NW and NWs with twin boundaries is dominated by the nucleation and propagation of parallel intrinsic stacking faults. This study will enrich the current understanding of the mechanical properties of NWs, which will eventually shed lights on their applications. Keywords Grain Boundary, Twin Boundary, Nanowire, Torsion, Molecular Dynamics 1. Introduction Metal and semiconductor nanowires (NWs) have been widely utilized as active components of nanoelectromechanical systems (NEMS) due to their extraordinary mechanical, electrical, optical and thermal properties, such as high frequency resonators, field effect transistors (FETs), and other devices [1]. Hence, a comprehensive understanding of the mechanical properties of NWs is increasingly required. There have been a number of experimental, theoretical and computational studies on the properties of NWs. On the experimental front, researchers have studied the mechanical behaviours of NWs under bending, tension, compression and vibration. On the theoretical and computational front, either surface-based extensions of continuum elasticity theory [2] or multi-scale computational techniques [3] has been employed to investigate the mechanical properties of NWs. Besides, molecular dynamics (MD) simulations has also being frequently adopted to explore structure-property relationship for NWs under different loading conditions [4-7]. It is noticed that most of current studies have focused on mono-crystalline NWs due to the decreased possibility of defects and flaws in nanoscale materials. However, recent experimental studies reveal that NWs also contain certain defects. For instance, metal NWs are found usually polycrystalline, containing grain boundaries (GBs) that transect the whole NW normal to its longitudinal axis into a bamboo structure [8]. Sansoz et al. [9] revealed that, twin boundaries (TBs) are ubiquitous for both synthesis and properties in nano-enhanced FCC metals. Therefore, understanding the influence from GBs or TBs to the properties of NWs is crucial to enhance/realize their applications. There have been a number of studies on the mechanical behaviours of defected
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