Mo 5 B 2 Si-type intermetallic phases M 5 (Pd/Pt) 2 Cd and M 5 Au 2 Zn ( M = Ca, Sr, Eu, Yb)

Abstract The intermetallic compounds M 5 (Pd/Pt) 2 Cd and M 5 Au 2 Zn ( M = Ca, Sr, Eu, Yb) were synthesized in sealed tantalum ampoules in a high-frequency furnace. Phase purity and crystallinity were increased by subsequent annealing in muffle furnaces. The compounds were studied by powder X-ray diffraction. They crystallize with the tetragonal Mo 5 B 2 Si-type structure, space group I 4/ mcm . The structures of Eu 5 Pd 2 Cd, Ca 5 Pt 1.93(1) Cd 1.07 , Eu 5 Pt 2.10(1) Cd 0.90 and Ca 5 Au 2.27(1) Zn 0.73 were refined from single-crystal X-ray diffractometer data. Refinements of the occupancy parameters indicated small homogeneity ranges originating from minor degrees of mixed occupancies on the 4 a and/or 8 h sites. The structures are intergrowth variants of W and AlB 2 -related slabs that stack in AB sequence. The striking coordination motifs (Eu 5 Pd 2 Cd as an example) are slightly compressed Eu1@Eu2 8 cubes, bi-capped square antiprisms Cd@Eu 10 and tricapped trigonal prisms Pd@Eu 8 Pd. 151 Eu Mössbauer spectra of Eu 5 Pd 2 Cd and Eu 5 Au 2 Zn confirm a divalent ground state for the europium atoms.