Ternary intermetallics with high zinc content: TT'_2Zn_(20) (T = Zr, Hf, Nb; T' = Mn, Fe, Ru, Co, Rh, Ni) with CeCr_2Al_(20)-type structure

摘要

Fourteen new compounds TT'_2Zn_(20) were prepared by reaction of the elemental components. They crystallize with the cubic CeCr_2Al_(20)-type structure (space group Fd3m, Z = 8), which was refined from single-crystal X-ray data of HfRu_2Zn_(20) (a = 1406.9(1) pm) and NbFe_2Zn_(20) (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 NbCo_2Zn_(20) (a = 1382.2(10 pm) was refined from X-ray powder data of 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.