Orientation-Dependent Structural Transition and Melting of Au Nanowires

Using molecular dynamics simulations with the quantum corrected Sutton-Chen type many-body potential, we have studied the thermal stability of Au nanowires along the [100], [110], and [111] crystallographic orientations during continuous heating. The bond pair analysis and Lindemann index are used to characterize the structural and thermal evolution of these nanowires. The results show that the critical temperatures of structural transition, melting, and fracture are dependent on the crystallographic orientation of Au nanowires. It is found that all the Au nanowires exhibit an inhomogeneous melting behavior from the surface into the interior. The structural transition from a fcc to hcp structure prior to surface premelting is closely associated with the activities of Shockley partial dislocations driven by the internal stress because of the thermal expansion of the nanowires with increased temperature. A comparison of the results of three types of nanowires indicates that the [110] nanowire possesses a better thermal and structural stability compared with other oriented nanowires, which helps to explain why Au nanowires possess a [110] preferred orientation during the experimental growth procedure.