Molecular Dynamics Study to Optimize the Preparation of Fe, Co, and Ni Nanoparticles as Catalysts for Growing Single-Walled Carbon Nanotubes

Maintaining nanoparticles (NPs) with identical catalytic properties is important for synthesizing single-walled carbon nanotubes with specific chiralities. The key to preparing NPs with consistent atomic stacking structures lies in preserving nucleation intermediates with uniform configurations and sizes. In this work, the physical mechanism underlying the improvement of structural similarity among intermediates is explored by investigating the structural transformation of M (M = Fe, Co, and Ni) NPs during the nucleation stage. The results show that the distance traversed by intermediates on the potential energy surface (i.e., the energetic displacement) not only determines the size distribution of intermediates but also influences their structural similarity. Furthermore, this distance can be tuned by adjusting the atomic feeding rate; hence, the size and atomic stacking structure of intermediates can be controlled. This work provides insight into achieving NPs with identical catalytic properties by modifying experimental parameters to tune atomic diffusion rates.