High-pressure modifications of CaZn2, SrZn2, SrAl2, and BaAl2: Implications for Laves phase structural trends

High-pressure forms of intermetallic compounds with the composition CaZn2, SrZn2, SrAl2, and BaAl2 were synthesized from CeCu2-type precursors (CaZn2, SrZn2, SrAl2) and Ba21Al40 by multi-anvil techniques and investigated by X-ray powder diffraction (SrAl2 and BaAl2), X-ray single-crystal diffraction (CaZn2), and electron microscopy (SrZn2). Their structures correspond to that of Laves phases. Whereas the dialuminides crystallize in the cubic MgCu2 (C15) structure, the dizincides adopt the hexagonal MgZn2 (C14) structure. This trend is in agreement with the structural relationship displayed by sp bonded Laves phase systems at ambient conditions.