Ternary Rare Earth Transition Metal Zinc Compounds

Forty eight new com pounds RT2Z n2o were prepared by annealing cold-pressed pellets o f the elem ental com ponents in an argon atm osphere. They crystallize with the cubic CeCr^Abo type structure (Fd3m , Z = 8), which was refined from single-crystal diffractom eter data o f TbFeiZn^o (a = 1411.1(1) pm), Y Ru2Z n2o (a = 1422.6(1) pm), D yRu2Z n2o (a = 1422.1(1) pm), G dC o2Z n2o (a = 1406.0(1) pm), D yR h2Zn2o (a = 1418.2(1) pm), andT m N i2Z n2o (a= 1401.6(1) pm) to conventional residuals varying between R = 0.011 and R 0.024. The com pounds have a tendency for tw inning, thus mim icking hexagonal symmetry, with the cubic [111] axis as the axis with the pseudohexagonal symmetry. M inor inconsistencies in the cell volum es of these com pounds indicate slight deviations from the ideal com position. N evertheless, the five atom ic sites o f this structure w ere found to be fully occupied within the error limits with the exception o f one zinc site o f T m N i2Zn2oThe coordination for the site o f the rare earth atom s is a Frank-K asper polyhedron with coordination num ber (CN) 16. The transition metal atoms occupy a site with icosahedral zinc coordination (CN 12). Two o f the three zinc sites are in pentagonal prism atic coordination o f zinc atom s, capped by rare earth and/or transition metal atom s (CN 12), while the third zinc site has 12 zinc neighbors form ing a hexagonal prism, which is capped by two rare earth atom s (CN 14).