Molecular-Dynamics Study of the Structural Dependence of the Young Modulus of Au Nanowires
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Molecular-Dynamics Study of the Structural Dependence of the Young Modulus of Au Nanowires S. Kameoka and K. Shintani Dept of ME & Intelligent Sys, Univ of Electro-Comm, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan E-mail: [email protected], URL: http://www.shintani.mce.uec.ac.jp/ ABSTRACT The deformation of Au nanowires of helical multi-shell (HMS) structures and the fcc structure under a tensile external force is addressed by molecular-dynamics simulation. The modified embedded-atom method (MEAM) potential is employed for calculating the interaction between Au atoms. At first, a model nanowire is equilibrated at a specified temperature. Next, the external force in the axial direction is imposed on the Au atoms at the ends of the nanowire. We conclude that the Young modulus of a Au nanowire depends on its atomic structure. INTRODUCTION The investigation of nanomaterials such as carbon nanotubes, fullerenes, semiconductor nanowires, and metallic nanowires is essential to the development of nanotechnology. They are suitable for use as nanoscale building blocks in opto-electronic devices and micro/nanoelectromechanical systems (MEMS/NEMS). For example, carbon nanotubes can be used as probe tips of scanning probe microscopes, nanomanipulators, and nanotweezers. On the other hand, Au nanowires are useful for biological applications because Au atoms can immobilize organic compound molecules having specific radicals. They are also useful for chemical applications because Au atoms can become catalysts for growth of semiconductor nanowire superlattices [1]. In order to realize these applications, it will be important to investigate the mechanical and electronic properties of such nanomaterials at nanoscale. Au nanowires have drawn much attention of researchers since a single-atom chain of gold atoms at a nanocontact between a scanning tunneling microscopic probe and a metal surface was observed [2]. They have some unique properties at nanoscale such as quantized conductance and long bond-length that are not observed for materials at macroscopic scale. It is probable that the mechanical behaviors of nanowires under external forces are different from those of the macroscopic materials. Suspended Au nanowires were fabricated in an ultra-high-vacuum (UHV) transmission electron microscope (TEM) with the electron beam thinning technique. It was revealed by high-resolution TEM that these nanowires have helical multi-shell (HMS) structures [3]. Carbon nanotubes have such helical structures, and they are metallic or semiconducting depending on the chirality. Similarly, metallic nanowires are expected to have also interesting physical properties due to their chirality. In this study, the molecular-dynamics (MD) simulations of elongation of Au nanowires are performed to investigate how the Young modulus of a Au nanowire depends on its atomic structure. Four model nanowires having HMS structures and the fcc structure are created for this purpose. We adopt the classical MD method with the modified embedded-atom method po
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