Yield Strength Asymmetry in Metal Nanowires

We performed atomistic simulations to study the yield mechanisms in gold nanowires. Perfect fcc gold nanowires all yield via the nucleation and propagation of {111}〈112〉 partial dislocations. The magnitude of the yield stress is much larger in tension versus compression for very small 〈100〉 nanowires, and this asymmetry is primarily due to the effects of surface stresses and different slip systems active during tensile and compressive yielding. Nanowires with a 〈111〉 orientation only show significant tension−compression asymmetry when defects exist in the wire prior to reverse compressive loading. The predictions may explain recent measurements regarding the yield of gold nanowires (see Marszalek, P. E.; Greenleaf, W. J.; Li, H. B.; Oberhauser, A. F.; Fernandez, J. M. PNAS 2000, 97, 6282).