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Most of the Rni(2) compounds (R=rare-earth element) do not crystallize in the cubic Laves phase structure (C15), but in a superstructure of C15 with ordered vacancies at the R sites. In the present work high pressure x-ray diffraction experiments on selected RNi2 compounds (R = Tb,Sm,Gd, and Y) are presented, showing that pressures of about 8�15 GPa lead to a disordering of the vacancies in all of them. Furthermore the studies show that the pressure-induced order-disorder transition is closely related to the earlier observed disordering of the vacancies at high temperatures between 430 (TbNi(2)) and 740 K (Yni(2)), and that there is a pronounced variation of the transition pressures and temperatures among the investigated compounds. The driving mechanism behind these transitions is discussed.

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Authors: LINDBAUM A, Vienna University of Technology, Institute for Experimental Physics, Vienna (AT);GRATZ E, Vienna University of Technology, Institute for Experimental Physics, Vienna (AT);HEATHMAN S, European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe (DE)
Bibliographic Reference: An article published in: Physical Review B, 65, (13), 134114 (1 April 2002)
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Record Number: 200316049 / Last updated on: 2003-03-13
Original language: de
Available languages: de