Molecular dynamics simulation of inert gas condensation of ternary Fe-Ni-Cr nanoparticles

Knowledge of condensation behavior of multimetallic nanoparticles is of great importance in prediction and advancing the understanding of synthesis, characterization and applications of metal nanoparticles. In this work, molecular dynamics simulations were performed to investigate the formation of a ternary Fe-Ni-Cr nanoparticle from a hot metastable vapor phase in Ar atmosphere. The configuration evolution reveals four distinct stages of probabilistic nucleation, surface growth, coalescence and agglomeration, coupled with severe surface segregation of Cr. The effect of the number of metal atoms on the nucleation, cluster growth and liquid-to-solid transition of the nanoparticles was studied as well. The finite system size has a negligible effect on the nucleation rate, while presents different cluster growth modes, i.e., surface growth for sub-nm clusters and aggregation for larger ones. Moreover, the cluster solidification begins from the inner region and proceeds gradually outwards to the surface, accompanying structural relaxation by forming lamellar FCC/HCP layers or multiple-fold twins. The solidification temperature exhibits a linear relationship with the inverse of the particle size, signifying the feasibility of the linear size-depression effect for the solidification of the nanoparticles. This work therefore provides an atomic understanding of inert gas condensation behavior and mechanisms of ternary Fe-Ni-Cr nanoparticles.