Deep trapping states for hydrogen in deformed iron

Kumnick, A. J.; Johnson, H. H.

doi:10.1016/0001-6160(80)90038-3

Cited by 445 publications

(185 citation statements)

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“…introduces low energy trapping sites within the lattice which retard the overall diffusion rate. [7][8][9] Because H is a light element, intrinsic processes in H diffusion are strongly influenced by its quantum mechanical behavior. At low temperatures quantum tunneling is expected to be the dominant mechanism.…”

Section: Introductionmentioning

confidence: 99%

Fully quantum mechanical calculation of the diffusivity of hydrogen in iron using the tight-binding approximation and path integral theory

2013

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We present calculations of free energy barriers and diffusivities as functions of temperature for the diffusion of hydrogen in α-Fe. This is a fully quantum mechanical approach since the total energy landscape is computed using a new self consistent, transferable tight binding model for interstitial impurities in magnetic iron. Also the hydrogen nucleus is treated quantum mechanically and we compare here two approaches in the literature both based in the Feynman path integral formulation of statistical mechanics. We find that the quantum transition state theory which admits greater freedom for the proton to explore phase space gives result in better agreement with experiment than the alternative which is based on fixed centroid calculations of the free energy barrier. We also find results in better agreement compared to recent centroid molecular dynamics (CMD) calculations of the diffusivity which employed a classical interatomic potential rather than our quantum mechanical tight binding theory. In particular we find first that quantum effects persist to higher temperatures than previously thought, and conversely that the low temperature diffusivity is smaller than predicted in CMD calculations and larger than predicted by classical transition state theory. This will have impact on future modeling and simulation of hydrogen trapping and diffusion.

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Section: Introductionmentioning

confidence: 99%

Fully quantum mechanical calculation of the diffusivity of hydrogen in iron using the tight-binding approximation and path integral theory

2013

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“…provide low energy trapping sites within the lattice and retard the overall diffusion. 13,[21][22][23][24][25][26] The existence of these traps plays an important role in the retention of hydrogen within the bulk, given the low solubility of hydrogen in iron. 1 Furthermore, when trapping occurs at interfaces such as matrix/second-phase particles, grain boundaries, microcracks, etc., the cohesive strength of these interfaces is compromised, thereby promoting decohesion and/or emission of dislocations.…”

Section: Introductionmentioning

confidence: 99%

Effect of atomic scale plasticity on hydrogen diffusion in iron: Quantum mechanically informed and on-the-fly kinetic Monte Carlo simulations

et al. 2008

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We present an off-lattice, on-the-fly kinetic Monte Carlo (KMC) model for simulating stress-assisted diffusion and trapping of hydrogen by crystalline defects in iron. Given an embedded atom (EAM) potential as input, energy barriers for diffusion are ascertained on the fly from the local environments of H atoms. To reduce computational cost, on-the-fly calculations are supplemented with precomputed strain-dependent energy barriers in defect-free parts of the crystal. These precomputed barriers, obtained with high-accuracy density functional theory calculations, are used to ascertain the veracity of the EAM barriers and correct them when necessary. Examples of bulk diffusion in crystals containing a screw dipole and vacancies are presented. Effective diffusivities obtained from KMC simulations are found to be in good agreement with theory. Our model provides an avenue for simulating the interaction of hydrogen with cracks, dislocations, grain boundaries, and other lattice defects, over extended time scales, albeit at atomistic length scales.

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“…Therefore, for these steels with a low-carbon martensitic structure, it seems to be likely that the dislocations with a high density, which were formed during the martensitic transformation, are the dominant trapping sites for hydrogen. Many studies [15][16][17] proved that dislocations are important trapping sites for hydrogen in deformed iron, and obtained the trap binding energy to be 25.6-59.9kJ/mol. The suggestion as stated above for martensitic alloy steels is in agreement with that for carbon steel [13] and also supports the Turnbull et al conclusions [4].…”

Section: Resultsmentioning

confidence: 99%