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Comptes Rendus Physique
Volume 9, n° 3-4
pages 409-417 (avril-mai 2008)
Doi : 10.1016/j.crhy.2007.09.019
The non-Arrhenius migration of interstitial defects in bcc transition metals
Migration de type non-Arrhenius des défauts interstitiels dans les métaux de transition de structure cubique centrée
 

Sergei L. Dudarev a, b,
a EURATOM/UKAEA Fusion Association, Culham Science Centre, Oxfordshire OX14 3DB, UK 
b Department of Physics, Imperial College, Exhibition Road, London SW7 2AZ, UK 

Correspondence to: EURATOM/UKAEA Fusion Association, Culham Science Centre, Oxfordshire OX14 3DB, UK.
Abstract

Thermally activated migration of defects drives microstructural evolution of materials under irradiation. In the case of vacancies, the activation energy for migration is many times the absolute temperature, and the dependence of the diffusion coefficient on temperature is well approximated by the Arrhenius law. On the other hand the activation energy for the migration of self-interstitial defects, and particularly self-interstitial atom clusters, is very low. In this case a trajectory of a defect performing Brownian motion at or above room temperature does not follow the Arrhenius-like pattern of migration involving infrequent hops separated by the relatively long intervals of time during which a defect resides at a certain point in the crystal lattice. This article reviews recent atomistic simulations of migration of individual interstitial defects, as well as clusters of interstitial defects, and rationalizes the results of simulations on the basis of solutions of the multistring Frenkel–Kontorova model. The treatment developed in the paper shows that the origin of the non-Arrhenius migration of interstitial defects and interstitial defect clusters is associated with the interaction between a defect and the classical field of thermal phonons. To cite this article: S.L. Dudarev, C. R. Physique 9 (2008).

The full text of this article is available in PDF format.
Résumé

La migration thermiquement activée des défauts ponctuels contrôle lʼévolution de la microstructure des matériaux sous irradiation. Pour la migration des lacunes la valeur de lʼénergie dʼactivation équivaut généralement à plusieurs fois la température absolue, et, la dépendance thermique du coefficient de diffusion est bien décrite par une loi de type Arrhenius. Cependant lʼénergie dʼactivation de la migration des auto-interstitiels isolés ou sous forme de boucle est très faible. Dans ce cas la trajectoire dʼun défaut effectuant un mouvement brownien à la température ambiante ou au-dessus ne suit pas une diffusion de type Arrhenius, cʼest-à-dire des sauts peu fréquents séparés par des durées relativement longues pendant lesquelles le défaut réside dans un site déterminé du cristal. Ce papier fait la revue des simulations atomiques récentes de la migration dʼauto-interstitiels isolés ou sous forme de boucle, et, rationalise les résultats de ces simulations sur la base des solutions du modèle « multi-corde » de Frenkel–Kontorova. Lʼapproche développée dans ce papier montre que lʼorigine de la migration de type non-Arrhenius dʼauto-interstitiels ou de boucles dʼinterstitiels est à associer à lʼinteraction du défaut considéré avec le champ classique des phonons dʼorigine thermique. Pour citer cet article : S.L. Dudarev, C. R. Physique 9 (2008).

The full text of this article is available in PDF format.

Keywords : Neutron irradiation, Interstitial defect, Transition metal

Mots-clés : Irradiation par neutrons, Défaut interstitiel, Métal de transition




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