Critical Role of Crystal Orientation and Temperature in Determining the Mechanical Properties and Failure Mechanisms of Gold Nanowires: Insights from Molecular Dynamics Simulations

Abstract The Molecular Dynamics simulations were performed using a parallel Molecular Dynamics code, LAMMPS. A model of Au nanowire was created with initial atomic positions corresponding to those of the bulk fcc Au lattice. The original length of the nanowire was 100 Å and the diameter was 40 Å. To simulate an infinitely long nanowire, periodic boundary conditions were applied in the Z direction. The system was first equilibrated using energy minimization using the Polak-Ribiere version of the conjugate gradient algorithm. The system was then brought to the thermal equilibrium with temperature variations of 150 K, 300 K, and 600 in the NVT ensemble. As temperature increases from 150 K to 600 K, tensile strength and Young’s modulus decline across all orientations due to increased atomic vibrations that weaken metallic bonds. Among the orientations tested, nanowires aligned with the original lattice (Z-axis <0 0 1>) exhibited the highest strength and stiffness at lower temperatures, suggesting greater robustness in this configuration. Notably, nanowires rotated 45° along the X or Y-axis demonstrated slightly better resilience to temperature-induced weakening, likely due to specific atomic arrangements in these orientations. Under tensile strain, nanowires with a 45° rotation around the Z-axis maintained a stable FCC structure up to 11.95% strain. Beyond this strain level, significant deformation occurred, characterized by the appearance of HCP regions and other structural deviations, which indicate a heightened risk of mechanical failure. In contrast, nanowires rotated around the X or Y-axis experienced structural transformations and complex dislocations at lower strain levels, underscoring a greater susceptibility to deformation and failure. These findings highlight the critical influence of temperature and crystallographic orientation on the mechanical behavior of gold nanowires.