Beschreibung:
The rare earth metal (RE)-magnesium-thallides REMgTl (RE = Y, La-Nd, Sm, Gd-Tm, Lu) were prepared from the elements in sealed tantalum tubes in a water-cooled sample chamber of a high-frequency furnace. The thallides were characterized through their X-ray powder patterns. They crystallize with the hexagonal ZrNiAl type structure, space group P62m, with three formula units per cell. Four structures were refined from X-ray single crystal diffractometer data: α = 750.5(1), c = 459.85(8) pm, wR2 = 0.0491, 364 F2 values, 14 variables for YMgTl; α = 781.3(1), c = 477.84(8) pm, wR2 = 0.0640, BASF = 0.09(2), 425 F2 values, 15 variables for LaMgTl; α = 774.1(1), c = 473.75(7) pm, wR2 = 0.0405, 295 F2 values, 14 variables for CeMgTl; a = 760.3(1), c = 465.93(8) pm, wR2 = 0.0262, 287 F2 values, 14 variables for SmMgTl. The PrMgTl, NdMgTl, GdMgTl, TbMgTl, and DyMgTl structures have been analyzed using the Rietveld technique. The REMgTl structures contain two cystallographically independent thallium sites, both with tri-capped trigonal prismatic coordination: Tl1Mg3RE6 and Tl2Mg6RE3. Together the magnesium and thallium atoms form three-dimensional [MgTl] networks with Mg-Mg distances of 327 and Mg-Tl distances in the range 299 - 303 pm (data for CeMgTl)