Molecular Dynamics Simulations of Au-Pt Alloy Nanowires: Effects of Strain Rate, Temperature, and Composition

Abstract

The mechanical properties exhibited by nanostructures of a metal alloy are significantly different from those exhibited by the same alloy in the bulk state. Molecular dynamics is a powerful simulation method to analyze the properties of metal alloy nanostructures. In this work, yield stress, elastic modulus, and modulus of resilience of Au-Pt alloy nanowires are studied using molecular dynamics, and how the temperature, the alloy composition, and the strain rate at which the nanowires are subjected to tension affect these properties have been analyzed. Results demonstrate that yield stress, elastic modulus, yield strain, and resilience modulus, deteriorate with temperature irrespective of applied strain rates of 0.0002 ps^-1 and 0.02 ps^-1. At low strain rates, the deformation mechanism involves cyclical yielding and recrystallization, whereas higher strain rates cause amorphization of the crystal structure. Increased strain rate causes higher yield stress, higher modulus of resilience, and lower modulus of elasticity. It is found that alloy nanowires with higher Au concentrations generally show a reduction in all mechanical properties. We observed that Au₇₅Pt_25, and Au₅₀Pt₅₀ nanowires yield just after commencement of elongation at 600K. Simulation results indicate that the absolute value of the potential energy of pure Au after conjugate-gradient minimization and thermal equilibration at 300K is the lowest whereas the absolute value of the potential energy of pure Pt is the highest at the same conditions. The simulation also shows that as the percentage of Pt increases in Au-Pt alloys, the absolute value of potential energy increases at the same conditions.