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0901-Ra22-19-Rb22-19.1

Atomistic study of the mechanical properties of one-dimensional nanomaterials K. Shintani, S. Kameoka, S. Sato, and Y. Kometani Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan E-mail: [email protected], URL: http://www.shintani.mce.uec.ac.jp/ ABSTRACT The mechanical properties of Au nanowires under a uniaxial load are investigated by molecular-dynamics simulation. The modified embedded-atom method (MEAM) potential is employed to calculate the interactions between Au atoms. Ten kinds of model nanowires with different cross-sections and axis directions are prepaired. The structural dependence and size effect of the Young’s moduli of Au nanowires are discussed. INTRODUCTION One-dimensional nanomaterials such as metallic nanowires and carbon nanotubes are suited for nanoscale building blocks in opto-electronic devices and micro/nano-electromechanical systems (MEMS/NEMS). Understanding their mechanical properties is essential in order to know how to design such building blocks. Much attention of researchers has been payed on metallic nanowires since quantized conductance through individual rows of suspended Au atoms was observed [1]. Supended Au nanowires were also processed in an ultra-high vacuum with the electron beam thinning technique, and these nanowires proved to have helical multi-shell (HMS) structures [2, 3]. Recently, the mechanical behaviors of Au nanowires with HMS structures have been studied using molecular-dynamics simulation with the tight-binding potential based on a second-moment approximation (TB-SMA) [4]. Accoding to this study, the Young’s modulus increases as the radius of the nanowire decreases. In the present study, we address the structural dependence and size effect of the Young's modulus of Au nanowires by using the molecular dynamics (MD) method with the modified embedded atom method (MEAM) potential [5]. Ten kinds of nanowire models with HMS structures and the face-centered cubic (fcc) structure are created. The uniaxial tensile forces are imposed on the nanowire models, and the stress-strain curves yield their Young's moduli. MODELS AND SIMULATION METHOD We prepared ten kinds of nanowire models as shown in table I. Models 1-1, 1-2, and 1–3 have HMS structures with n, n’, and n” helical atom rows where n, n’, and n” are the numbers of atoms in the outer, middle, and inner shells, respectively. A helical shell of a nanowire can imaginatively be constructed by rolling a triangular-lattice sheet [6]. The helical shell is uniquely specified by the chiral vector Ch which is expressed by the basic translational vectors a and b in the triangular lattice as Ch =pa+qb, where p and q are intergers and called chiral indices, and the chiral vector Ch is expressed as (p,q). The chiral indices of the outer shell of Model 1-1, the outer and inner shells of Model 1-2, and the outer and middle shells of Model 1-3 are (4,3), (5,6), (2,2), (7,8), and (4,4), respectively. The numbers o