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Analysis of a carbon dimer bound to a vacancy in iron using density functional theory and a tight binding model

: Paxton, A.T.; Elsässer, C.

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Physical Review. B 87 (2013), Nr.22, Art. 224110, 10 S.
ISSN: 0163-1829
ISSN: 1098-0121
ISSN: 0556-2805
European Commission EC
FP7-NMP; 263335; MultiHy
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IWM ()

Recent density functional theory (DFT) calculations by Först have predicted that vacancies in both low and high carbon steels have a carbon dimer bound to them. This is likely to change the thinking of metallurgists in the kinetics of the development of microstructures. While the notion of a C2 molecule bound to a vacancy in Fe will potentially assume a central importance in the atomistic modeling of steels, neither a recent tight binding (TB) model nor existing classical interatomic potentials can account for it. Here we present a TB model for C in Fe, based on our earlier work for H in Fe, which correctly predicts the structure and energetics of the C2 dimer at a vacancy in Fe. Moreover the model is capable of dealing with both concentrated and dilute limits of carbon in both -Fe and -Fe as comparisons with DFT show. We use both DFT and TB to make a detailed analysis of the dimer and to come to an understanding as to what governs the choice of its curious orientation within the vacancy.