Molecular dynamics simulation of the growth and diffusion mechanisms of Fe–Cu bimetallic nanoparticles

In accordance with the molecular dynamic simulation and nudged elastic band method, the surface diffusion and growth of Fe–Cu nanoparticles were studied, respectively, using Large-scale Atomic/Molecular Massively Parallel Simulator code. Results showed that a single Cu adatom diffused on the surface of the Fe substrate mainly via the hopping mechanism and nearly did not exchange with the substrate atoms. In the Cu substrate, when interfacet diffusion of a Fe adatom on the surface was activated, the system energy evidently decreased after the exchange mechanism was chosen. At low temperatures, the metastable core–shell structure of FeshellCucore nanoparticles was obtained by simulating the deposition of Fe on Cu substrate. For the growth of Cu on Fe substrate, FecoreCushell nanoparticles could be formed and they gradually evolved into Wulff-like structures with depositing Cu atoms. The Monte Carlo calculation further showed that the stable configuration of Fe–Cu nanoparticles is FecoreCushell when the concentration of Cu atoms is small. With the increase of Cu atomic ratio (enough to cover the surface), the quasi-Janus was the stable structure in Fe–Cu nanoparticles.