13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Chirality and Size Dependent Elastic Properties of Silicene Nanoribbons under Uniaxial Tension Yuhang Jing1,2,*, Yi Sun1, Hongwei Niu1, Jun Shen2 1 Department of Astronautical Science and Mechanics, Harbin Institute of Technology, Harbin 150001, China 2 School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China * Corresponding author: jingyh@hit.edu.cn Abstract The mechanical properties of silicene are investigated using ab initio calculation and molecular dynamics simulations with different empirical potentials. The simulation results show that the calculated Young’s modulus of bulk silicene with EDIP model is consistent with the ab initio calculations. The chirality has a significant effect on the critical strain and stress of bulk silicene under uniaxial tension. In addition, the Young’s modulus depends strongly on the chirality and size of the silicene nanoribbon. The fracture process of a silicene nanoribbon is also studied. Keywords Silicene, Young’s modulus, Chirality and Size effects 1. Introduction Graphene, which is a two-dimensional (2D) atomic layer of graphite, forms the basis of both 3D graphite and 1D carbon nanotubes. Since the discovery of graphene, graphene has attracted a worldwide attraction due to its extraordinary mechanical and electronic properties and potential applications [1-5]. The silicon analogue of graphene, the so called silicene, also attracts considerable scientific interest [6-8]. Recently, the possible growth of silicene nanoribbons on Ag (100), Ag (110), and Ag (111) substrates has been reported [9-11]. The electronic properties of silicene have also been investigated theoretically [12-14], some of which have been shown to be similar to those of graphene [12]. Thus, it can be expected that silicene can have the remarkable characters as graphene. Similar to graphene nanoribbons, the electronic properties of silicene nanoribbons are dependent of the structural size and chirality. Armchair silicene nanoribbons are semiconducting while the zigzag silicene nanoribbons are metallic when the width of the ribbons is broader [15]. However, compared with graphene, silicene have more potential applications in future nanoscale devices due to its compatibility with conventional Si-based electronic technology. Mechanical properties of nanoscale structures need to be understood in detail to enable design of high-performance and reliable micro/nanoelectromechanical systems (MEMS/NEMS) [16]. From a theoretical viewpoint, many correlative theoretical predictions have been performed in recent years and the attentions are mainly paid on the microstructural and electronic properties of the silicene [12-15]. The theoretical investigation of the mechanical properties of the silicene is also necessary and timely. However, the mechanical properties of silicene have not been reported so far. Therefore, in this work, ab initio calculations are performed to obtain robust predictions of the mechanical properties of the silicene, and then we investigate the chirality and size effects on the elastic properties of silicene nanoribbons using molecular dynamics (MD) simulations. 2. Simulation details We employ ab initio calculations in order to obtain robust predictions of the mechanical properties of silicene using SIESTA code [17] and check different empirical potentials’ accuracy. By means of extensive optimization, a user-defined double zeta plus polarization (DZP) basis set is constructed for the silicene. The Perdew-Burke-Ernzerhof (PBE) formulation of the generalized gradient approximation (GGA) for the exchange and correlation functional is used in the calculation to account for the electron-electron interactions. The k-grid sampling of 16×16×1 for the silicene, together with a meshcutoff of 200 Ry for the system are used in the calculation. Small stress is applied along zigzag or armchair direction of silicene and then relax the geometry until the forces on each atom are less than 0.01 eV Å-1.
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