Crystalline liquid and rubber-like behavior in Cu nanowires.

Via in situ TEM tensile tests on single crystalline copper nanowires with an advanced tensile device, we report here a crystalline-liquid-rubber-like (CRYS-LIQUE-R) behavior in fracturing crystalline metallic nanowires. A retractable strain of the fractured crystalline Cu nanowires can approach over 35%. This astonishing CRYS-LIQUE-R behavior of the fracturing highly strained single crystalline Cu nanowires originates from an instant release of the stored ultralarge elastic energy in the crystalline nanowires. The release of the ultralarge elastic energy was estimated to generate a huge reverse stress as high as ~10 GPa. The effective diffusion coefficient (D(eff)) increased sharply due to the consequent pressure gradient. In addition, due to the release of ultrahigh elastic energy, the estimated concomitant temperature increase was estimated as high as 0.6 Tm (Tm is the melting point of nanocrystalline Cu) on the fractured tip of the nanowires. These factors greatly enhanced the atomic diffusion process. Molecular dynamic simulations revealed that the very high reverse stress triggered dislocation nucleation and exhaustion.