Molecular dynamics study of the ordering of carbon in highly supersaturated alpha-Fe

CW Sinclair and M Perez and RGA Veiga and A Weck, PHYSICAL REVIEW B, 81, 224204 (2010).

DOI: 10.1103/PhysRevB.81.224204

A recently developed Fe-C interatomic potential has been used to investigate carbon in highly supersaturated alpha iron with an emphasis on the possible ways in which carbon can arrange itself on the octahedral sites of the tetragonally distorted alpha-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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