The C–C pair in the vicinity of a bcc Fe bulk vacancy: electronic structure and bonding

Simonetti, S.; Pronsato, M.E.; Brizuela, G.; Juan, Alfredo

doi:10.1002/pssb.200642410

Cited by 9 publications

(5 citation statements)

References 32 publications

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“…11 The binding energy for the Va 1 C 1 complex, E b ͑Va 1 C 1 ͒, is in good agreement with previous theoretical results. 17,[28][29][30] In contrast, current experimental results range appreciably, 0.4ഛ E b ͑Va 1 C 1 ͒ ഛ 1.1 eV, varying with experimental technique and sample preparation details. [31][32][33][34] The magnitude of E b ͑Va 1 C 1 ͒ predicted from resistivity measurements on low-temperature irradiated pure and carbon-doped bcc Fe is comparatively high ͑1.1 eV͒.…”

Section: A Point-defect Clusters: Formation and Abundancementioning

confidence: 72%

Effects of vacancy-solute clusters on diffusivity in metastable Fe-C alloys

et al. 2010

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Diffusivity in defected crystals depends strongly on the interactions among vacancies and interstitials. Here we present atomistic analyses of point-defect cluster ͑PDC͒ concentrations and their kinetic barriers to diffusion in ferritic or body-centered-cubic ͑bcc͒ iron supersaturated with carbon. Among all possible point-defect species, only monovacancies, divacancies, and the PDC containing one vacancy and two carbon atoms are found to be statistically abundant. We find that the migration barriers of these vacancy-carbon PDCs are sufficiently high compared to that of monovacancies and divacancies. This leads to decreased self-diffusivity in bcc Fe with increasing carbon content for any given vacancy concentration, which becomes negligible when the local interstitial carbon concentration approaches twice that of free vacancies. These results contrast with trends observed in fcc Fe and provide a plausible explanation for the experimentally observed carbon dependence of volume diffusion-mediated creep in ferritic ͑bcc͒ Fe-C alloys. Moreover, this approach represents a general framework to predict self-diffusivity in alloys comprising a spectrum of point-defect clusters based on an energy-landscape survey of local energy minima ͑formation energies governing concentrations͒ and saddle points ͑activation barriers governing mobility͒.

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Section: A Point-defect Clusters: Formation and Abundancementioning

confidence: 72%

Effects of vacancy-solute clusters on diffusivity in metastable Fe-C alloys

et al. 2010

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“…Silica is a naturally occurring material, comprising silicate tetrahedra (SiO 4 ) in the crystalline form of quartz; it is the most abundant material in the Earth's crust and the key component of fiberoptic and dielectric-thin-film communication platforms. It is well known that water reduces the strength of silica through several mechanisms, including hydrolytic weakening of quartz due to interstitial water [24][25][26] and stress corrosion cracking of amorphous silica due to surface water [17,[19][20][21]. This interaction is representative of a broader class of chemomechanical degradation of material strength, including stress corrosion and hydrogen embrittlement in metals, and enzymatic biomolecular reactions.…”

Section: Diving In To Rough Energy Landscapes Of Alloys Glasses Andmentioning

confidence: 98%

“…The energy landscape of such Fe crystals is thus relatively smooth, notwithstanding the magnetic spin state of the atoms, and the activation barriers for nucleation of vacancies within the lattice can be determined directly via density functional theory (DFT) [3,[17][18][19][20][21]. The diffusion of single vacancies within the lattice must overcome an activation barrier, but in this case the energetic barrier of the diffusive unit process-atomic hopping to adjacent lattice sites-is defined by transition pathways that are essentially limited to < 100 > and < 111 > crystallographic directions.…”

Section: Diving In To Rough Energy Landscapes Of Alloys Glasses Andmentioning

confidence: 99%

Chemomechanics of complex materials: challenges and opportunities in predictive kinetic timescales

Vliet

2008

Sci Model Simul

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What do nanoscopic biomolecular complexes between the cells that line our blood vessels have in common with the microscopic silicate glass fiber optics that line our communication highways, or with the macroscopic steel rails that line our bridges? To be sure, these are diverse materials which have been developed and studied for years by distinct experimental and computational research communities. However, the macroscopic functional properties of each of these structurally complex materials pivots on a strong yet poorly understood interplay between applied mechanical states and local chemical reaction kinetics. As is the case for many multiscale material phenomena, this chemomechanical coupling can be abstracted through computational modeling and simulation to identify key unit processes of mechanically altered chemical reactions. In the modeling community, challenges in predicting the kinetics of such structurally complex materials are often attributed to the socalled rough energy landscape, though rigorous connection between this simple picture and observable properties is possible for only the simplest of structures and transition states. By recognizing the common effects of mechanical force on rare atomistic events ranging from molecular unbinding to hydrolytic atomic bond rupture, we can develop perspectives and tools to address the challenges of predicting macroscopic kinetic consequences in complex materials characterized by rough energy landscapes. Here, we discuss the effects of mechanical force on chemical reactivity for specific complex materials of interest, and indicate how such validated computational analysis can enable predictive design of complex materials in reactive environments.

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“…In a previous work, we have reported that the addition of a C atom in a Fe bcc matrix which contains a vacancy decreases the strength of the local Fe-Fe bond to about 78% of its original value. This bond weakening is a consequence of the C-Fe bond that is formed at the expense of Fe-Fe neighbour bondings [14].…”

Section: Introductionmentioning

confidence: 99%

A computational study of the carburization phenomena in a Fe–Ni alloy

Simonetti

Moro

Brizuela

et al. 2008

J. Phys. D: Appl. Phys.

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Massive carburization can occur in metallic service components due to operating conditions. The changes in the microstructure result in severe embrittlement of the material leading to a loss of corrosion resistance. In this paper, a first step in the study of the electronic structure and bonding that occur during carburization phenomena has been performed. The interaction between a carbon atom and a Fe50Ni50 alloy containing a vacancy has been studied by ASED-MO cluster calculations, firstly in a vacancy region and then on the FeNi(1 1 1) surface. The minimum energy position for the C atom in the vacancy region was found to be at 1.19 Å from the vacancy centre. The addition of a C atom in the FeNi matrix containing a vacancy decreases the strength of the local Fe–Fe bond to about 80% of its original bulk value. This bond weakening is mainly a consequence of the C–Fe interaction. On the other hand, the minimum energy position of the C atom on the FeNi(1 1 1) was found to be at 1.60 Å from the surface. The principal interaction is again C–Fe. The C-surface bonding is achieved mainly at the expense of the weakening of the Fe–Ni nearest neighbours bond to C, which decreases to about 52%.

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The C–C pair in the vicinity of a bcc Fe bulk vacancy: electronic structure and bonding

Cited by 9 publications

References 32 publications

Effects of vacancy-solute clusters on diffusivity in metastable Fe-C alloys

Effects of vacancy-solute clusters on diffusivity in metastable Fe-C alloys

Chemomechanics of complex materials: challenges and opportunities in predictive kinetic timescales

A computational study of the carburization phenomena in a Fe–Ni alloy

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