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A combination of ab initio total-energy calculations and high-pressure x-ray diffraction experiments has been used to study the phase stability of Y-based 1:2 compounds. The motivation for these investigations was to clarify the origin of the change of the structure among the YT(2) compounds (T = 3d transition element) between the neighbouring elements Ni (YNi(2): defect superstructure of cubic Laves phase C15) and Cu (YCu(2): orthorhombic CeCu(2) type structure). As a test of the ab initio calculations the cubic YAl(2) Laves phase compound has been included in the investigations. The ab initio calculations confirm the reversal of the relative stabilities of the CeCu(2) and C15 phases in YCu(2) and YNi(2) and give also the correct results for YAl(2). Furthermore a pressure-induced structural transition is predicted for YCu(2). The high-pressure x-ray experiments show that there is very good agreement between the calculated and the measured pressure dependence of the lattice parameters of YCu(2) up to about 10 GPa. Above 10 GPa the structure starts to become irreversibly amorphous. This instability may be a hint at the structural phase transition predicted by the calculations.

Additional information

Authors: LINDBAUM A, Vienna University of Technology, Institute for Experimental Physics (AT);GRATZ E, Vienna University of Technology, Institute for Experimental Physics (AT);HAFNER J, Vienna University of Technology, Institute for Theoretical Physics and Centre for Computational Materials Science (AT);HEATHMAN S, JRC Karlsruhe (DE)
Bibliographic Reference: Article: Journal Physics: Condensed Matter, Vol. 10 (1998) pp. 2933-2945
Record Number: 199811181 / Last updated on: 1998-10-09
Original language: en
Available languages: en