Study of crystallization pathway and dynamical heterogeneity in iron nanoparticle

Abstract

In this paper, crystallization pathway and dynamical heterogeneity (DH) in iron nanoparticle (NP) have been investigated in detail for spherical samples containing 5000 atoms, which were obtained by the molecular dynamics simulation based on Pak–Doyama potential. The crystallization was analyzed through pair radial distribution function, angle distribution, parameter [Formula: see text]F[Formula: see text] and transition to different x-types, where x is the bcc, fcc-hcp, ico, 14 or 12. We found that transitions to bcc-type do not happen arbitrarily at any location in NP, but instead they are concentrated in a nonequilibrium region. The crystallization pathway comprises of intermediate states between amorphous and crystalline ones. At the early stage, a large cluster of Cryst-atom formed is located in a middle layer of NP. Then, this cluster grows up and the parameter [Formula: see text]F[Formula: see text] for it increases rapidly. At the final stage, the cluster of Cryst-atom is located in a well-equilibrium region covering a major part of NP. It is found that the structure of amorphous and crystalline NPs is strongly heterogeneous and consists of separate regions with different local microstructure. This indicates the DH in NP. We also found that there is a connection between local structures and DH in NP.