Electronic bonding characteristics of hydrogen in bcc iron: Part I. Interstitials

Itsumi, Yoshio; Ellis, Donald E

doi:10.1557/jmr.1996.0280

Cited by 40 publications

(25 citation statements)

References 19 publications

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“…The advantage of this approach is its transparency and simplicity which, for example, allows one to avoid the convergence problem associated with the Hartree-Fock or Density Functional Theory (DFT) methods. This EHT study is closely related to the recent ab initio calculation of the H 2 adsorption on a 32-atom cluster [5].…”

Section: Introductionsupporting

confidence: 53%

Reduction of Nitroaromatic Compounds on the Surface of Metallic Iron: Quantum Chemical Study

Zilberberg

Pelmenschikov

McGrath

et al. 2002

IJMS

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Abstract:The initial reduction steps of nitroaromatic compounds on the surface of metallic iron have been studied theoretically using nitrobenzene (NB) as a representative of nitroaromatic compounds. The quantum chemical cluster approximation within the semiempirical Neglect of Diatomic Differential Overlap for Metal Compounds method was applied to model the Fe(110) crystallographic surface, taken as a representative reactive surface for granular iron. This surface was modeled as a 39-atom two-layer metal cluster with rigid geometry. The associative and dissociative adsorption of nitrobenzene was considered. Based on our quantum chemical analysis, we suggest that the direct electron donation from the metal surface into the π * orbital of NB is a decisive factor responsible for subsequent transformation of the nitro group. Molecularly adsorbed NB interacts with metal iron exclusively through nitro moiety oxygens which occupy tri-coordinated positions on surface The charge transfer from metal to NB of approximately 2 atomic units destablizes the nitro group. As a result, the first dissociation of the N-O bond goes through a relatively low activation barrier. The adsorbed nitrosobenzene is predicted to be a stable surface species, though still quiet labile.

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Section: Introductionsupporting

confidence: 53%

Reduction of Nitroaromatic Compounds on the Surface of Metallic Iron: Quantum Chemical Study

Zilberberg

Pelmenschikov

McGrath

et al. 2002

IJMS

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“…Itsumi et al carried out electronic structure calculations for body-centered cubic (bcc) Fe with interstitial H by using the first-principles discrete variational method. [80] They reported that the volume expansion is to be expected and the Fe-H interaction occurs mainly via the Fe 4s and H 1s orbitals. A charge transfer of ∼ 0.6e from Fe to H leads to a decrease in the metallic bond strength.…”

Section: Interstitial Effect On Magnetic Properties and Magnetic Entrmentioning

confidence: 98%

Magnetic entropy change involving martensitic transition in NiMn-based Heusler alloys

Hu¹,

Shen²,

Sun³

2013

Chinese Phys. B

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Our recent progress on magnetic entropy change (∆S) involving martensitic transition in both conventional and metamagnetic NiMn-based Heusler alloys is reviewed. For the conventional alloys, where both martensite and austenite exhibit ferromagnetic (FM) behavior but show different magnetic anisotropies, a positive ∆S as large as 4.1 J·kg −1 ·K −1 under a field change of 0-0.9 T was first observed at martensitic transition temperature T M ∼ 197 K. Through adjusting the Ni:Mn:Ga ratio to affect valence electron concentration e/a, T M was successfully tuned to room temperature, and a large negative ∆S was observed in a single crystal. The −∆S attained 18.0 J·kg −1 ·K −1 under a field change of 0-5 T. We also focused on the metamagnetic alloys that show mechanisms different from the conventional ones. It was found that post-annealing in suitable conditions or introducing interstitial H atoms can shift the T M across a wide temperature range while retaining the strong metamagnetic behavior, and hence, retaining large magnetocaloric effect (MCE) and magnetoresistance (MR). The melt-spun technique can disorder atoms and make the ribbons display a B2 structure, but the metamagnetic behavior, as well as the MCE, becomes weak due to the enhanced saturated magnetization of martensites. We also studied the effect of Fe/Co co-doping in Ni 45 (Co 1−x Fe x ) 5 Mn 36.6 In 13.4 metamagnetic alloys. Introduction of Fe atoms can assist the conversion of the Mn-Mn coupling from antiferromagnetic to ferromagnetic, thus maintaining the strong metamagnetic behavior and large MCE and MR. Furthermore, a small thermal hysteresis but significant magnetic hysteresis was observed around T M in Ni 51 Mn 49−x In x metamagnetic systems, which must be related to different nucleation mechanisms of structural transition under different external perturbations.

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“…Cette modification de la structure électronique locale des atomes de métal, combinée à une augmentation de la distance interatomique, affecte directement les forces de cohésion du réseau. Dans le cas des métaux de transition tels que le fer, cet effet se traduit par une diminution des forces de cohésion [4].…”

Section: Données Physiquesunclassified

“…L'absorption d'hydrogène conduit à un affaiblissement des liaisons métal-métal par modification de l'environnement électronique des atomes [4,[60][61][62]. Ce phénomène, qui est à l'origine de l'effet fragilisant de l'hydrogène, est d'autant plus marqué que la concentration locale en hydrogène est grande.…”

Section: Décohésion Associée Aux Interactions éLectroniques Hydrogèneunclassified

L'hydrogène dans les matériaux métalliques en relation avec les interactions plasticité-environnement

Chêne

2009

PlastOx 2007 - Mécanismes Et Mécanique Des Interactions Plasticité - Environnement

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Résumé. L'objectif de cet article est de faire une revue synthétique des données de la littérature qui permettent de caractériser le comportement de l'hydrogène dans les matériaux métalliques et plus particulièrement les effets d'endommagement associés à l'hydrogène en relation avec les interactions plasticité-environnement. Dans cette présentation générale nous nous sommes limités au comportement de l'hydrogène dans les matériaux de structure tels que les alliages base fer et base nickel.Les principaux points abordés dans cette présentation sont : -des généralités sur l'absorption de l'hydrogène dans ces alliages : diffusion, perméation, piégeage, -une courte revue des principaux effets d'endommagement associés à l'absorption d'hydrogène, -quelques remarques spécifiques aux interactions hydrogène-plasticité.

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Electronic bonding characteristics of hydrogen in bcc iron: Part I. Interstitials

Cited by 40 publications

References 19 publications

Reduction of Nitroaromatic Compounds on the Surface of Metallic Iron: Quantum Chemical Study

Reduction of Nitroaromatic Compounds on the Surface of Metallic Iron: Quantum Chemical Study

Magnetic entropy change involving martensitic transition in NiMn-based Heusler alloys

L'hydrogène dans les matériaux métalliques en relation avec les interactions plasticité-environnement

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