Atomistic treatment of periodic gold nanowire array nanofasteners under shear loading

Abstract

Comprehensive molecular dynamics simulations are conducted to unravel the mechanics and mechanisms associated with the strength and fracture behavior of a highly ordered gold nanowire (Au-NW) array of a pair of nanofasteners (nanoconnectors) under externally applied shear strain. Large-scale atomic/molecular massively parallel simulator (LAMMPS and embedded atom method were adopted to model the atomic interactions of a number of neighboring nanofasteners. This was affected via the use of a periodic simulation box around a pair of highly ordered nanotube arrays to minimize the cost of the computations. Energy minimization using a conjugate gradient algorithm was first performed and followed by atomic relaxation to achieve an equilibrated configuration under the canonical ensemble of constant temperature and volume. The relaxed equilibrated configuration of the nanofastener was then subjected to an externally applied shear strain at a rate of per nanosecond under the canonical ensemble. Our results reveal the importance of the morphology and the overlap depth of the mating nanowire arrays upon the mechanical and fracture behavior of the nanofastener under shear loading. Our work also disclosed the phenomenon of multiple contacts of some displaced nanowires with their neighbors even after their fracture leading to multiple cold-welds with added redundancy to the nanofastener. Finally, in this research, we identified the locations of dislocation emissions and the resulting fracture processes that govern the mechanical integrity and ultimately the functionality of the Au-NW connector. The proposed highly ordered alignment, as conceived numerically herein, can yield a peak stress two to three times higher than that corresponding to a random alignment reported in a previous study. The Au-NW connector also exhibited resistance to fracture, even in cases where small overlap depth is considered in joint bonding. The nanoconnector was also tested at high temperatures (up to 450 K). Our results show that the rising temperature only leads to a minor reduction in the load transmitted by the nanoconnector.

Nanotwinning and tensile behavior in cold-welded high-entropy-alloy nanowires

“…The as-created MD geometry consists of two cylindrical nanocrystals that are separated one lattice constant away side-by-side. As previously demonstrated, the mechanical performance of the bonded nanocrystal pair is not sensitive to the separation distance as long as it is sufficient for contact [34,37]. The original coldwelding approach for individual nanowires as proposed by Lu et al [1] did not require applying current or external force.…”

“…In recent years, atomistic simulations have been widely used as a powerful tool to investigate all kinds of structural performance regarding various nanostructures [23][24][25][26][27][28][29][30][31][32][33][34]. Our atomistic simulations here are conducted by using the software package LAMMPS [35].…”

“…To reduce computational cost, the two paired nanowires are represented by two cuboid or cylindrical nanocrystals. The same geometry has been adopted recently for Au nanowires [7,8,34,37]. The as-created MD geometry consists of two cylindrical nanocrystals that are separated one lattice constant away side-by-side.…”

Molecular dynamics simulations of cold welding of nanoporous amorphous alloys: effects of welding conditions and microstructures

“…The results showed that the van der Waals attraction transmitted through the connecting surface results in the size effect of the cold-welded nanocrystals. Besides 1D nanowires, the cold welding technique can also be used in complex nano-systems, such as nano-fasteners, 10 nanoribbons, 11 nanocomposites, 12 nano-assemblies, 13 and nanoporous materials. 14…”

“…The results showed that the van der Waals attraction transmitted through the connecting surface results in the size effect of the cold-welded nanocrystals. Besides 1D nanowires, the cold welding technique can also be used in complex nano-systems, such as nano-fasteners, 10 nanoribbons, 11 nanocomposites, 12 nano-assemblies, 13 and nanoporous materials. 14 Amorphous alloys lack atomic arrangement with long-range order and, thus, exhibit high strength, high elasticity, superior soft magnetic properties, and outstanding corrosion resistance.…”