Size effect on cold-welding of gold nanowires investigated using molecular dynamics simulations

The size effect on the cold-welding mechanism and mechanical properties of Au nanowires (NWs) in head-to-head contact are studied using molecular dynamics simulations based on the second-moment approximation of the many-body tight-binding potential. The results are discussed in terms of atomic trajectories, slip vectors, stress, radial distribution function, and weld strength ratio. Simulation results show that during the cold-welding process, a few disordered atoms/defects in the jointing area rearrange themselves and transform into a face-centered cubic crystalline structure. With an increase in contact between the two NWs, dislocations gradually form on the (111) slip plane and then on a twin plane, leading to an increase in the lateral deformation of 4-nm-wide NWs. The effect of structural instability increases with decreasing NW width, making the alignment of the two NWs more difficult. The elongation ability of the welded NWs increases with increasing NW width. Smaller NWs have better weld strength.