Elucidating the role of extended surface defects at Fe surfaces on CO adsorption and dissociation

Chakrabarty, Aurab; Bentria, El Tayeb; Omotayo, Salawu Akande; Bouhali, O.; Mousseau, Normand; Becquart, Charlotte; El-Mellouhi, Fedwa

doi:10.1016/j.apsusc.2019.05.278

Cited by 11 publications

(7 citation statements)

References 25 publications

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“…Force and velocities are computed using the three potentials (a) ReaxFF-2012, (b) RPOIC-2017, and (c) our extended-ReaxFF. MD simulations using ReaxFF-2012 (Figure a) evolve in a similar way to our previous work . It is clear from the final frame that, in the course of the simulation, several events of CO dissociation occurred, followed by carbide complex formation causing the supersaturation of the surface.…”

Section: Resultsmentioning

confidence: 53%

“…Figure a shows a snapshot of the surface after 300 ps, where the beginning of the formation of C–C chains and the reconstruction of the iron surface induced by the surrounding C atoms can be noticed. We showed, however, in our latest study that step edges that can be generated after surface reconstruction provide even lower dissociation barriers of 0.54 eV, the iron reconstruction on the surface provides a step edge-like environment that may contribute to the higher dissociation/diffusion rate in the 30% case.…”

Section: Discussionmentioning

confidence: 74%

“…In the course of this later simulation, it is not possible to observe the well-known mechanisms of CO adsorption, tilt, and dissociation. 32 The speedy CO dissociation we obtained looks unrealistic in such a short simulation time (taking into consideration that the CO dissociation barrier of the Fe (110) surface is ∼0.8 eV) 31 and led to the complete diffusion of all C and O atoms into the bulk. It is noticeable that C prefers to relax in high coordination positions, causing the first layers of the iron slab to become highly loaded with O and C (Figure 3b).…”

Section: Resultsmentioning

confidence: 95%

“…MD simulations using ReaxFF-2012 (Figure 3a) evolve in a similar way to our previous work. 31 It is clear from the final frame that, in the course of the simulation, several events of CO dissociation occurred, followed by carbide complex formation causing the supersaturation of the surface. No carbon diffusion into the iron bulk can be noticed, whereas oxygen diffusion reaches up to the fourth layer.…”

Section: Resultsmentioning

confidence: 98%

“…The computed barriers are in agreement with the well-known CO dissociation and C diffusion computed from density functional theory (DFT) calculations and give us confidence on the continuity of energies. 3,31 The Fe−C bonding in the bulk, however, needs further improvement as the carbon atom occupies pseudo-octahedral sites. More enhancement on the extended-ReaxFF will be conducted in the future as the ReaxFF parameterization is out of the scope of this work.…”

Section: Resultsmentioning

confidence: 99%

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Capturing the Iron Carburization Mechanisms from the Surface to Bulk

et al. 2020

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Reactive force field molecular dynamics is a powerful tool to simulate large-scale reactive events such as catalytic reactions and metallic corrosion, including the carburization or so-called metal dusting corrosion. Building on a vast set of reactive force field parameters, it aims to reduce the gap between computational and experimental observations. However, the production of different versions of reactive force field parameter sets in the past 2 decades demonstrates the challenges faced by developers when attempting to describe correctly and at the same time a broad range of environments, such as the kinetics of CO adsorption, dissociation, and carbon diffusion in iron systems. This has limited the ability of these force fields to capture the competing phenomena governing complex evolution such as the carburization of iron responsible for metal dusting corrosion. In this work, we demonstrate that it is possible to treat very different environments in an integrated way by expanding the ReaxFF parameter set, creating an environment-specific description. This approach enables us to capture both metallic surface-induced dissociation of carbon-containing gases such as carbon monoxide (CO) and atomic carbon bulk diffusion in iron systems within the same simulation setup so far unreachable with previously available force fields. Employing this extended-ReaxFF to describe a cell containing a gas mixture of carbon monoxide and argon reacting with an Fe(110) surface, we fully capture at the same time competing carburization reaction/diffusion processes on both the surface and the bulk. Analysis of the radial distribution function and charge density maps shows a variety of carbon bonds at different stages/layers, highlighting the diversity of the mechanisms captured while using our extended-ReaxFF. Interestingly, at a CO coverage higher than 0.7 monolayers, the atomic arrangement of the iron atoms is sufficiently altered to cause surface reconstruction leading to a significant increase in carbon diffusion. Moreover, we are able to observe and quantify the diffusion of Fe from the bulk toward the upper coke layer, computationally elucidating the slow but continuous coke formation reported experimentally, opening a wide range of opportunities to model various stages of iron carburization mechanisms.

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Section: Resultsmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

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