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LaCu(2) is the only compound among the RCU(2) series (R from La to Lu, and Y) which crystallizes in the hexagonal AIB(2)-type structure, whereas the other compounds show the orthorhombic CeCu(2)-type structure. In agreement with ab initio calculations our high-pressure x-ray diffraction experiments show that LaCu(2) transforms at relatively low pressures to the CeCu(2)-type structure, which can be regarded as a low-symmetry variant of the AlB(2) -type structure.

To investigate the stability of the CeCu(2)-type structure we performed high-pressure x-ray diffraction experiments on YCU2 using argon as the pressure transmitting medium. These experiments showed in contrast to an earlier study that the CeCu(2) structure is stable at least up to the highest attained pressure of 35 GPa. The tendency for amorphization at pressures above 10 GPa, as observed in the earlier study, was probably due to the non-hydrostatic conditions of the pressure transmitting medium, showing that the CeCu(2)-type compounds are very sensitive to non-hydrostatic compression. A transition to the MgCu2-tyPe structure (cubic Laves phase) at about 28 GPa, as predicted by the ab initio calculations, has not been observed.

Additional information

Authors: LINDBAUM ET AL, JRC, ITU Karlsruhe, (DE);KRESSE ET AL, Technische University of Wien, Vienna (AT);ROTTER ET AL, Technische Universitat, Dresden (DE);BEHR G, Institut fur Festkorperphysik, Dreden (DE);LE BIHAN T, European Synchroton Grenoble (FR);SVOBODA P, Charles University, Ke Kerlovu, Praha (CZ)
Bibliographic Reference: Article: Journal of Physics: Condensed Matter, 12(2000) pp 3219-3228
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