Diffusion properties of Fe-C systems studied by using kinetic activation-relaxation technique

Oscar A. Restrepo, Normand Mousseau, Fadwa El-Mellouhi, Othmane Bouhali, Mickaël Trochet, Charlotte S. Becquart

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Diffusion of carbon in iron is associated with processes such as carburization and the production of steels. In this work, the kinetic activation-relaxation technique (k-ART) - an off-lattice self-learning kinetic Monte Carlo (KMC) algorithm - is used to study this phenomenon over long time scales. Coupling the open-ended ART nouveau technique to generate on-the-fly activated events and NAUTY, a topological classification for cataloging, k-ART reaches timescales that range from microseconds to seconds while fully taking into account long-range elastic effects and complex events, characterizing in details the energy landscape in a way that cannot be done with standard molecular dynamics (MD) or KMC. The diffusion mechanisms and pathways for one to four carbon interstitials, and a single vacancy coupled with one to several carbons are studied. In bulk Fe, k-ART predicts correctly the 0.815 eV barrier for a single C-interstitial as well as the stressed induced energy-barrier distribution around this value for 2 and 4 C interstitials. For vacancy-carbon complex, simulations recover the DFT-predicted ground state. K-ART also identifies a trapping mechanism for the vacancy through the formation of a dynamical complex, involving C and neighboring Fe atoms, characterized by hops over barriers ranging from ∼0.41 to ∼0.72 eV that correspond, at room temperature, to trapping time of hours. At high temperatures, this complex can be broken by crossing a 1.5 eV barrier, leading to a state ∼0.8 eV higher than the ground state, allowing diffusion of the vacancy. A less stable complex is formed when a second C is added, characterized by a large number of bound excited states that occupy two cells. It can be broken into a V-C complex and a single free C through a 1.11 eV barrier.

Original languageEnglish
Pages (from-to)96-106
Number of pages11
JournalComputational Materials Science
Volume112
DOIs
Publication statusPublished - 1 Feb 2016

Fingerprint

Activation
Kinetics
Chemical activation
Vacancy
Vacancies
activation
Carbon
kinetics
interstitials
carbon
Kinetic Monte Carlo
Ground state
Trapping
trapping
Ground State
Time Scales
ground state
Steel
Energy barriers
Self-learning

Keywords

  • Activated dynamics
  • Corrosion
  • Defects
  • Diffusion
  • Fe-C
  • Kinetic Monte Carlo
  • Steel

ASJC Scopus subject areas

  • Materials Science(all)
  • Chemistry(all)
  • Computer Science(all)
  • Physics and Astronomy(all)
  • Computational Mathematics
  • Mechanics of Materials

Cite this

Diffusion properties of Fe-C systems studied by using kinetic activation-relaxation technique. / Restrepo, Oscar A.; Mousseau, Normand; El-Mellouhi, Fadwa; Bouhali, Othmane; Trochet, Mickaël; Becquart, Charlotte S.

In: Computational Materials Science, Vol. 112, 01.02.2016, p. 96-106.

Research output: Contribution to journalArticle

Restrepo, Oscar A. ; Mousseau, Normand ; El-Mellouhi, Fadwa ; Bouhali, Othmane ; Trochet, Mickaël ; Becquart, Charlotte S. / Diffusion properties of Fe-C systems studied by using kinetic activation-relaxation technique. In: Computational Materials Science. 2016 ; Vol. 112. pp. 96-106.
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