A recently developed Fe-C interatomic potential has been used to investigate carbon in highly supersaturated ␣ iron with an emphasis on the possible ways in which carbon can arrange itself on the octahedral sites of the tetragonally distorted ␣-iron lattice. Focusing particularly on the composition Fe 16 C 2 , the embedded atom method potential used gives the same ground-state structure of Fe 16 C 2 as density-functional-theory calculations. Moreover, when computing C-C interactions between two carbon atoms at 0 K with energy minimization, the preferred separation distance corresponds exactly to the octahedral site positions expected in Fe 16 C 2 . It has been shown with molecular dynamics that the carbon atoms in Fe 16 C 2 change how they order on octahedral sites during heating and during cooling. Finally, when investigating the interaction energy of Fe 1−x C x for different carbon compositions, it is found that there is a clear minimum at x = 0.11 for the fully ordered structure, corresponding to Fe 16 C 2 composition. The results of these calculations are discussed with particular reference to carbon ordering in ferrous martensite.

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