Structural stability and compressibility behaviour of dialuminides of cerium and gadolinium under high pressure

High pressure X-ray diffraction experiments were done up to similar to 23 G Pa on CeAl2 and up to similar to 16 GPa on GdAl2. Both the systems are foun d to be stable in the cubic Laves phase up to the pressures investigated an d show anomalous compressibility behaviour as a function of pressure. In th e case of GdAl2, the anomaly is quite subtle, however, in the cerium compou nd it is quite pronounced between 2 and 6 GPa with no volume collapse. The compressibility behaviour of these compounds is discussed in the light of c hanges occurring in the electronic structure. For this purpose electronic s tructure calculations have been performed as a function of reduced volume. The extended range of stability of the MgCu2 type cubic Laves phase compoun ds under the action of pressure is inferred from the present work. (C) 1999 Elsevier Science Ltd. All rights reserved.