Ternary intermetallics with high zinc content:: TT′2Zn20 (T = Zr, Hf, Nb; T′ = Mn, Fe, Ru, Co, Rh, Ni) with CeCr2Al20-type structure

Fourteen new compounds TT'Zn-2(20) were prepared by reaction of the elemental components. They crystallize with the cubic CeCr2Al20- type structure (space group Fd (3) over barn, 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 R-F = 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. (C) 2001 Academic Press.