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, Ainsi, s'il a été constaté qu'une pression d'hydrogène de 1 kbar permet d'augmenter la stoechiométrie de x = 4,2 à x = 5, il n'existe aucune étude concernant son évolution à plus haute pression d'hydrogène

, Première étude sous pression d'hydrogène

, Une première expérience sur YFe 2 H 4.2 sous pression d'hydrogène a été menée jusqu, p.35

R. Gpa, . En, and . Préliminaires, Si une maille orthorhombique permet d'ajuster correctement toutes les données entre 8 et 35 GPa, la structure pourrait être tétragonale entre 8 et 17 GPa (c ? b ? 2). Lorsque la pression augmente, les paramètres a et b paraissent avoir un comportement "classique

, Un calcul de stoechiométrie, mené par comparaison avec les équations d'état de YFe 2 et YFe 2 H 5 , permet de tracer la figure 8.2, sur laquelle on peut voir que la stoechiométrie de YFe 2 H x augmente avec un facteur de l'ordre de 0,06 atome/GPa. Cette augmentation spontanée de la stoechiomé

, YFe 2 H x semble se charger en hydrogène au fur et à mesure que la pression augmente, avec l'élongation du paramètre c, conséquence de la diffusion d'atomes d'hydrogène de manière anisotrope

. Dans-le-cas-de-mg, BH 4 ) 2 , la diffusion d'hydrogène finit par atteindre un palier [63], et il serait intéressant de voir si cela est aussi le cas dans l'hydrure YFe 2 H x . Des calculs ab initio, sur le modèle de ceux initiés pour le système Fe-Al-H

, Première étude sous pression d'hydrogène 151

, 1 (a) Paramètres de maille de YFe 2 H x , obtenus par un ajustement Le Bail des données de diffraction, avec les mailles Fd3m (cubique) et Pnm2 (orthorhombique) respectivement. (b) Équation d'état de YFe 2 H x (triangles roses), comparée aux données issues de, FIGURE, vol.8, issue.2

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