Molecular dynamics study of strain-induced diffusivity of nitrogen in pure iron nanocrystalline

• Mean square displacement was used to calculate coefficients of nitrogen diffusion in pure iron under strain conditions.
• Molecular dynamics shows that nitrogen diffusion is affected by the compression and tensile strain applied to the iron–nitrogen single crystal.
• Higher diffusion coefficients of nitrogen were obtained along [0001] crystal direction under compression.
• Diffusion is higher under compressive strain than tensile strain.

In the present study, the self-diffusion process of nitrogen in pure iron nanocrystalline under strain conditions has been investigated by Molecular Dynamics (MD). The interactions between particles are modeled using Modified Embedded Atom Method (MEAM). Mean Square Displacement (MSD) of nitrogen in iron structure under strain is calculated. Strain is applied along [112̄0] and [0001][0001] directions in both tensile and compression conditions. The activation energy and pre-exponential diffusion factor for nitrogen diffusion is comparatively high along [0001][0001] direction of compressed structure of iron. The strain-induced diffusion coefficient at 973 K under the compression rate of 0.001 Å/ps along [0001][0001] direction is about 6.72E−14 m22/s. The estimated activation energy of nitrogen under compression along [0001][0001] direction is equal to 12.39 kcal/mol. The higher activation energy might be due to the fact that the system transforms into a more dense state when compressive stress is applied.