Structural evolution of nanoparticles under picosecond stress wave consolidation

In this work, large-scale atomistic modeling is conducted to explore a relatively cold consolidation process: nanoparticles compressed by a stress wave from a sacrificial layer that is ablated by a picosecond laser. The temperature, stress, atomic configuration, and crystallinity are studied in detail to understand the structural behaviors under extreme compression. Study of the temperature and structure evolution reveals that compression and reconstruction are cold processes indeed. Despite the destruction–reconstruction process, the material temperature is below its melting point. The stress wave consolidation leads to a final nanocrystalline structure. An orientation–radial distribution function (ODF) is designed to study the status of the nanocrystalline structure in detail. Compared with the radial distribution function, the ODF provides a 2D picture of the material structure, and uncovers details of material twisting and destruction. Smaller nanoparticles are easier to consolidate and reconstruct, and the final structure is more like amorphous and structural defects are observed. The center part of the particle retains its original crystalline structure while cold-consolidation primarily occurs in the particle–particle contact region. The number of reconstructed atoms is higher when the particle size is smaller, and strong structure twisting in space is observed. 2014 Elsevier B.V. All rights reserved.