Bibliographic Details
| Title: |
Atomic-scale Ab-initio study of the Zr-H system: I. Bulk properties |
| Authors: |
Domain, C.1 Christophe.Domain@edf.fr, Besson, R.2, Legris, A.2 |
| Source: |
Acta Materialia. Aug2002, Vol. 50 Issue 13, p3513. 14p. |
| Subjects: |
Zirconium, Hydrogen analysis, Hydrides, Kirkendall effect |
| Abstract (English): |
Bulk properties of the Zr-H system were studied in the framework of the density functional theory. The local density approximation (LDA) is found to be insufficient for a proper description of interactions between Zr and H atoms and the generalized gradient approximation (GGA) is required. In αZr, H atoms preferentially occupy tetrahedral (T) sites at low temperatures, and can be regarded as being independent of each other up to very short distances, except for repulsive interactions between dumbbells in the same interstitial site. The Zr density of electronic states is perturbed by the presence of H, which induces the emergence of localized states. H diffusion occurs along the c→ axis preferentially in octahedral (O) sites, and in the basal plane by alternate jumps into T and O sites. In the γ(ZrH), δ (ZrH1.5) and ϵ(ZrH2) hydrides, H-H interactions cannot be neglected, the nearly equal formation energies of these compounds indicate that their relative stabilities probably depend on mechanical and thermal contributions to free energies, and in fcc Zr, H atoms tend to adopt planar arrangements for compositions close to ZrH. [ABSTRACT FROM AUTHOR] |
| Abstract (French): |
Nous avons e´tudie´ les proprie´te´s volumiques du syste`me Zr-H par des calculs s’appuyant sur la me´thode de la fonctionnelle de densite´. L’approximation de la densite´ locale (LDA) se re´ve`le insuffisante pour une description correcte des interactions entre atomes Zr et H, qui requiert l’approximation du gradient ge´ne´ralise´ (GGA). Dans Zrα, les atomes H occupent pre´fe´rentiellement les sites te´trae´driques (T) a` basse tempe´rature et se comportent de manie`re inde´pendante les uns des autres jusqu’a` des distances tre`s courtes, les seules interactions de´tecte´es concernant les doublets dans un meˆme site interstitiel. La densite´ d’e´tats e´lectroniques de Zr est modifie´e par la pre´sence de H, qui provoque l’apparition d’e´tats localise´s. La diffusion de H a lieu essentiellement via les sites O le long de l’axe c→, et par sauts alterne´s entre sites T et O dans le plan basal. Dans les hydrures γ(ZrH), δ(ZrH1.5) et ϵ(ZrH2), les interactions entre atomes H ne peuvent eˆtre ne´glige´es, les e´nergies de formation quasi e´gales de ces compose´s indiquent que leurs stabilite´s relatives de´pendent probablement des contributions thermiques et me´caniques a` l’e´nergie libre, et dans Zr cfc, les atomes H ont tendance a` adopter des arrangements planaires pour des compositions proches de ZrH. [ABSTRACT FROM AUTHOR] |
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| Database: |
Engineering Source |
