Development of Fe-C interatomic potential for carbon impurities in alpha-iron

TQ Nguyen and K Sato and Y Shibutani, COMPUTATIONAL MATERIALS SCIENCE, 150, 510-516 (2018).

DOI: 10.1016/j.commatsci.2018.04.047

Two versions of interatomic potentials for iron-carbon system based on the analytic bond-order potential formalism were developed and tested on diffusion of carbon in body-centered cubic (BCC) iron. By using these potentials, we found that carbon diffuses from octahedral site to the next nearest neighbor octahedral site via tetrahedral site, with energy barriers of 0.74 and 0.70 eV, respectively. These values are in good agreement with the transition from octahedral site to octahedral site via tetrahedral site with energy barriers of about 0.81-0.87 eV, observed in experiment. Other theoretical works found similar diffusion mechanism with energy barriers of about 0.72-0.92 eV. We also verified the transferability of the newly developed potential in the study of the effect of carbon on the body-centered cubic/face-centered cubic (BCC/FCC) phase transition in iron following the phase transition in the Bain mechanism. We found that the presence of carbon leads to the decrease of the BCC to FCC transformation energy barrier, consistent with first-principles calculations. Thus, the new potentials can be good candidates for modeling carbon diffusion and the transformation processes in iron-carbon alloys.

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