Ternary Intermetallics with High Zinc Content: TT2Zn20 (T=Zr, Hf, Nb; T=Mn, Fe, Ru, Co, Rh, Ni) with CeCr2Al20-Type Structure

Fourteen new compounds TTʹ2Zn20 were prepared by reaction of the elemental components. They crystallize with the cubic CeCr2Al20-type structure (space group Fd m, Z=8), which was refined from single-crystal X-ray data of HfRu2Zn20 (a= 1406.9(1) pm) and NbFe2Zn20 (a=1387.9(1) pm) to conventional residuals of R=0.018 and R=0.022 for 268 and 144 structure factors, respectively, and 17 variable parameters each. The structure of the compound NbCo2Zn20 (a=1382.2(1) pm) was refined from X-ray powder data to RF=0.031. The occupancy parameters have practically the ideal values for all five atomic sites of the three structures. The largest voids in this structure are octahedral with a size similar to those in the structure of elemental zinc.