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This article presents the use of neutron and X-ray diffraction techniques on both single crystal and polycrystalline samples to examine the symmetry of the unit cell of the organometallic compound uranium tris(cyclopentadienyl)chlorine, U(C(5)H(5))(3)Cl, as a function of temperature below 300 K. Two phase transitions are shown to occur. The first, at 245 K, results in a change of space group but the monoclinic symmetry is retained. The second, at 78 K, results in the material becoming triclinic Important differences are observed between the results obtained with neutron and X-ray diffraction. The latter fail to show clear evidence for the transition at 78 K. This is a consequence of the different penetration depths of the two radiations. Calorimetric data confirm the presence of the 245 K transition.

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Authors: RAISON P ET AL., JRC Karlsruhe (DE);DELAPALME A, CEA, CEN Saclay, Gif-sur-Yvette (FR);KIAT J M, CEA, CEN Saclay, Gif-sur-Yvette (FR);SCHWEISS P, Forschungszentrum Karlsruhe GmbH (DE);KANELLAKOPULOS B, Forschungszentrum Karlsruhe GmbH (DE);GONTHIER-VASSAL A, Université Paris-Sud, Laboratoire de Chimie-Physique des Materiaux Amorphes, Orsay (FR);BROWN P J, Institute Laue-Langevin, Grenoble (FR)
Bibliographic Reference: Article: Molecular Physics
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