Molecular dynamics study of nitrogen diffusion in nanocrystalline iron.

To obtain a deeper understanding of the production of advanced high-nitrogen steels, the diffusivity of nitrogen in bcc iron was investigated at the nanoscale by molecular dynamics (MD) simulation using the modified embedded-atom method (MEAM) interatomic potential. The diffusivity of nitrogen was calculated by mean square displacement (MSD) at different temperatures (773-1473 K) and nitrogen concentrations (0.23, 0.77, and 1.50 wt.%). The results show that the diffusion coefficient increases with temperature and decreases with increasing nitrogen concentration. The temperature dependence of the diffusion coefficient according to the Arrhenius equation was obtained. Activation energies and pre-exponential factors for different nitrogen concentrations were derived from the diffusion coefficient.