Shock-induced localized amorphization in metallic nanorods with strain-rate-dependent characteristics

Classical force-field simulations were used to study the tensile shock-induced response of metallic nanorods. The nanorods were found to amorphize at strain-rate amorphization limits of 1.6% ps(-1) for a 4.0-nm-diameter platinum (Pt) nanorod and 1.2% ps(-1) for a 4.0-nm-diameter gold (Au) nanorod, with a length-to-diameter ratio of 3. Highly localized necking was observed at mid-depth of the nanorods at about 2.0% ps(-1). As the strain rates were increased further, the neck bifurcated away from the mid-depth toward the nanorod ends, resulting in multiple necks at 4.0% ps(-1) and 3.0% ps(-1) for Pt and Au, respectively. At strain rates of above 6.0% ps(-1), end delamination took place. The longitudinal wave propagation equation was adequate to explain and predict the location of the appearance of necks along the nanorod.