13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- nano-joining and assembly conforming 3D networks are still in very early stages. Accordingly, in the present work we invoke concept of hierarchical nano-joining to propose new architectures comprised of fullerenes and SWCNTs. We present a systematical atomistic simulation study on the mechanical properties of the novel 3D spanned-fullerene nanotruss architecture. 2. Model and Methodology We adopt a CNT (6,6) and a giant fullerene C372 with D2d molecular symmetry as parent bricks for constructing novel covalent bonded 3D nano-truss systems. As illustrated in Figure 1, 3D nanostructures are built from a fullerene C372. Three atomic pairs are added as patches (red atoms in Figure 1b) in the face of fullerene (green atoms in Figure 1a and 1b) to create an open-cage cluster with a terminal. This terminal is able to coaxially dock a (6,6) CNT segment (purple atoms in Figure 1c), forming three octagon rings dispersed at the junction. The truss-like 3D network with an all-sided coalescence of fullerenes with (6,6) CNTs is finally created as shown in Figure 1d, resembling a body center cubic (bcc) lattice. The mechanical responses of as-generated 3D nano-truss under tension are systematically investigated with respect to the connection CNT length N varying from 0 to 10. Figure 1 (a) (d) Schematic illustration for constructing the unit of 3D spanned-fullerene nanotube nanotruss. (e) Perspective of 3D architecture models with 3×3×3 unit cells. The full atomistic simulations are carried out using LAMMPS software package capable of running on large computing clusters. The adaptive intermolecular reactive empirical bond-order (AIREBO) potential [21] is used for carbon atomic interactions in the simulations. The cutoff parameter for the REBO part of the potential is set to be 2.0 Å as described by Shenderova [22] in order to avoid the spuriously high bond forces and nonphysical phenomenon during the fracture process. As-constructed architecture models with 3×3×3 unit cells (Figure 1e) are first quasi-statically relaxed by minimizing the total potential energy through a conjugate gradient method. The mechanical loads of uniaxial tension under deformation-control as our previous study [23], are performed on 3D equilibrated structures until complete rupture of each specimen. The samples are deformed with a reasonable strain rate 0.0001/ps based on Nosé-Hoover thermostat. Stresses and strain are calculated every 1000 steps. The nominal strain parallel to the direction of deformation is defined as
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