Hydrogen redistribution in the solid solutions ZrV2Dx, 2.2≤x≤2.7.: II. Structure of the intermediate phase: ‘Lattice liquid crystal’. A neutron-diffraction study |
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Authors: | A. V. Irodova G. Andre F. Bouree |
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Affiliation: | a Russian Research Center ‘Kurchatov Institute’, 123182, Moscow, Russia b Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay, 91191, Gif sur Yvette, France |
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Abstract: | We have studied the crystal structure of the uncommon phase with k=0 in ZrV2Dx, 2.2<x<2.5, which is an intermediate between the hydrogen-disordered phase and two hydrogen superstructures, ZrV2D<2 with k=(1/2 1/2 1/2) and ZrV2D>2.7 with k=(001). This phase is a primary superstructure combining the features of the disordered phase and, depending on the hydrogen concentration, one or another superstructure with k≠0. Its lattice (translational symmetry) is the same as in the disordered phase, which is k=0. Simultaneously, the lattice sites (the hydrogen arrangement in them) are prototypes of the sites of the subsequent superstructure with k≠0. Specifically, each site of the primary superstructure with k=0 is a mix of the sites with different spatial orientation of the superstructure with k≠0. In this sense the primary superstructure can be considered as a ‘lattice liquid crystal’ whereas usual superstructure with k≠0 is a ‘lattice crystal’. In addition, we have determined the crystal structure of the ‘ordered’ phase with k=(001) in ZrV2D2.73. It is a transitional state between the primary superstructure and the regular superstructure with the same k. |
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Keywords: | Hydrogen absorbing materials Metal hydrides Crystal structure Neutron diffraction |
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