DFT calculations of hydrogen diffusion and phase transformations in magnesium

Klyukin, Konstantin; Shelyapina, Marina G.; Fruchart, D.

doi:10.1016/j.jallcom.2015.05.039

Cited by 34 publications

(35 citation statements)

References 58 publications

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“…In Mg, the barrier for T-T jump is about 0.1 eV, much lower than that for T-O (~0.23 eV) and O-O (~0.21 eV) jumps23. In Ti, the barrier of T-T jump (0.061 eV) is nearly an order lower than that of T-O (0.424 eV) and O-O (0.625 eV) jumps2.…”

Section: Discussionmentioning

confidence: 88%

“…More recently, starting from Fick’s law and considering the balanced flux between equilibrated tetrahedral and octahedral sites, in Klyukin et al . an expression was derived for H diffusivity in hcp metal as23:…”

Section: Resultsmentioning

confidence: 99%

“…The hopping rates obtained from DFT calculations need to be incorporated into either analytical theories or other modeling methods such as kinetic Monte Carlo (KMC) to predict diffusivity. In the literature, several theories have been proposed for H diffusion in hcp crystals2223. These theories give different predictions for H diffusivity.…”

mentioning

confidence: 99%

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Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

Zhang

Jiang

Bai

2017

Sci Rep

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This report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in α-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in α-Zr and Zircaloy is dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along is found to be slightly higher than that along , with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in α-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins.The diffusion of hydrogen in hcp metals has attracted extensive research interests for both its scientific merit and technological importance. It is the rate-limiting step for solid hydrogen storage in Mg based alloys 1 and for mechanical property degradation in Ti 2 and Zr alloys 3 . For instance, Zr-based alloys such as Zircaloy2 and Zircaloy4 (denoted as Zircaloy) are widely used as the cladding of fuel rods in nuclear reactors for their excellent corrosion resistance and very low absorption cross-section of thermal neutrons. During their service time, these alloys operate in extremely harsh environments, combining high temperatures and corrosive coolants such as water. In light water reactors, Zircaloy claddings directly contact coolant water, with a local temperature at the interface of about 400 °C. Consequently, Zircaloy react with water, producing an oxide layer at the interface and hydrogen (H), of which a substantial fraction infiltrates into the cladding interior 3 . Due to the low solubility of H in α -Zr, which is the main component of claddings, hydrides precipitate in the cladding matrix 4-6 . Hydride formation can detrimentally affect the cladding integrity primarily in two ways. First, the formation of hydrides reduces the fracture toughness of the cladding matrix 7,8 , increasing the probability of fuel failure when fuel-cladding mechanical interaction (PCMI) occurs during fuel operation. Second, upon cyclic thermal and mechanical loadings, hydrides can dissolve and reorient. During used-fuel storage, fracture may propagate via the so-called delayed-hydride-cracking (DHC) mechanism, which is induced by the dissolving of matrix hydrides and their subsequent re-formation at crack tips 3,9 . To mitigate thes...

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Section: Discussionmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

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Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

Zhang

Jiang

Bai

2017

Sci Rep

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“…This requires considering the so-called phonon calculations that is still very time consuming and when realized, it usually applies well to rather small cells with a high symmetry only. Besides, for many metal hydrides this correction is not very important, e.g., with MgH 2 it is only for a few percents [37]. However, in transition metal hydrides it can be comparable and even greater than the value of the activation energy.…”

Section: Hydrogen Diffusion Studied By Dftmentioning

confidence: 99%

“…This leads to correct the formulas of the diffusion coefficient. For example, for hydrogen diffusion between two tetrahedral (T) sites via a metastable octahedral (O) site in the hcp lattice one has [37]:…”

Section: Hydrogen Diffusion Studied By Dftmentioning

confidence: 99%

Hydrogen diffusion in metal-hydrogen systems via NMR and DFT

Shelyapina

Vyvodtceva

Klyukin

et al. 2015

International Journal of Hydrogen Energy

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Influence of Defects on the Stability and Hydrogen‐Sorption Behavior of Mg‐Based Hydrides

Novaković

Kurko

et al. 2019

ChemPhysChem

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This review deals with the destabilization methods for improvement of storage properties of metal hydrides. Both theoretical and experimental approaches were used to point out the influence of various types of defects on structure and stability of hydrides. As a case study, Mg, and Ni based hydrides has been investigated. Theoretical studies, mainly carried out within various implementations of DFT, are a powerful tool to study mostly MgH 2 based materials. By providing an insight on metalhydrogen bonding that governs both thermodynamics and hydrogen kinetics, they allow us to describe phenomena to which experimental methods have a limited access or do not have it at all: to follow the hydrogen sorption reaction on a specific metal surface and hydrogen induced phase transformations, to describe structure of phase boundaries or to explain the impact of defects or various additives on MgH 2 stability and hydrogen sorption kinetics. In several cases theoretical calculations reveal themselves as being able to predict new properties of materials, including the ways to modify Mg or MgH 2 that would lead to better characteristics in terms of hydrogen storage. The influence of ion irradiation and mechanical milling with and without additives has been discussed. Ion irradiation is the way to introduce a well-defined concentration of defects (Frankel pairs) at the surface and subsurface layers of a material. Defects at the surface play the main role in sorption reaction since they enhance the dissociation of hydrogen. On the other hand, ball-milling introduce defects through the entire sample volume, refine the structure and thus decrease the path for hydrogen diffusion. Two Severe Plastic Deformation techniques were used to better understand the hydrogenation/dehydrogenation kinetics of Mg-and Mg 2 Nibased alloys: Equal-Angular-Channel-Pressing and Fast-Forging. Successive ECAP passes leads to refinement of the microstructure of AZ31 ingots and to instalment therein of high densities of defects. Depending on mode, number and temperature of ECAP passes, the H-sorption kinetics have been improved satisfactorily without any additive for mass H-storage applications considering the relative speed of the shaping procedure. A qualitative understanding of the kinetic advanced principles has been built. Fast-Forging was used for a "quasiinstantaneous" synthesis of Mg/Mg 2 Ni-based composites. Hydrogenation of the as-received almost bi-phased materials remains rather slow as generally observed elsewhere, whatever are multiple and different techniques used to deliver the composite alloys. However, our preliminary results suggest that a synergic hydrogenation / dehydrogenation process should assist hydrogen transfers from Mg/Mg 2 Ni on one side to MgH 2 / Mg 2 NiH 4 on the other side via the rather stable a-Mg 2 NiH 0.3 , acting as in-situ catalyser.

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DFT calculations of hydrogen diffusion and phase transformations in magnesium

Cited by 34 publications

References 58 publications

Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

Hydrogen diffusion in metal-hydrogen systems via NMR and DFT

Influence of Defects on the Stability and Hydrogen‐Sorption Behavior of Mg‐Based Hydrides

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