Regensburg 2000 – scientific programme

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M: Metallphysik

M 5: Struktur und Umwandlung I

M 5.3: Talk

Monday, March 27, 2000, 18:00–18:15, H16

Structural stability of LaCu₂ and YCu₂ studied by high pressure x-ray diffraction and ab-initio total energy calculations — •Andreas Lindbaum¹, Steve Heathman¹, Georg Kresse², Martin Rotter³, Ernst Gratz⁴, Astrid Schneidewind³, Guenther Behr⁵, Karsten Litfin¹, Tristan Le Bihan⁶, and Pavel Svoboda⁷ — ¹Joint Research Centre (European Commission), Postfach 2340, D-76125 Karlsruhe — ²Inst. f. Materialphysik, Uni Wien — ³Inst. f. Angewandte Physik, TU Dresden — ⁴Inst. f. Experimentalphysik, TU Wien — ⁵IFW Dresden — ⁶ESRF Synchrotron, Grenoble — ⁷Department of Electronic Structures, Charles University Prag

LaCu₂ is the only compound among the RCu₂ series

(R from La to Lu, and Y), which crystallises in the

hexagonal AlB₂ -type structure, whereas the other

compounds show the orthorhombic CeCu₂ -type

structure. In agreement with ab-initio calculations

our high pressure x-ray diffraction experiments show

that LaCu₂ transforms at relatively low pressures

to the CeCu₂ -type structure, which can be regarded

as a distorted low-symmetry variant of the AlB₂ -type

structure.

For investigating the stability of the CeCu₂ -type

structure we performed high pressure x-ray diffraction

experiments on YCu₂ using argon as pressure transmitting

medium. These experiments showed that the CeCu₂ structure

is stable at least up to the highest attained pressure of 35 GPa.