Er6F3oOSn, trigonal, R3 (No. 148), a = 14.475(2) Â, c = 9.894(1) Â, V= 1795.3 Â , Ζ = 3, R^F) = 0.036, RvfF) = 0.067, T= 293 K. Source of material Light pink colored powder samples and single crystals of the title compound were obtained by heating intimate mixtures of appropriate amounts of SrF2, and ErF3 (99.9% Alpha) at 1400 Κ for 4 days in a sealed platinum tube followed by s low cooling ( 5 0 K/h). Discussion The structure of S n E r ^ a t ) is isotypic to Na7ZreF3i [1] and the so-called rh-s phases in the systems REF2/SEF3 (RE = Eu, Yb, Sm) [2] and can be considered as an anion rich derivate of the CaF2 type structure. The higher anion/cation ratio, 31/13 instead of 26/13 in CaF2, is formally obtained by a transformation of an empty F8 cube into a F12 cuboctahedra [3], which is centered by an additional F(6) occupying its position statistically. The Er atoms are square antiprismatically surrounded by 8 F [d(Er-F) = 223 pm — 234 pm] with an additional F(6) capping one of the square faces [rf(Er-F(6)) = 259 pm]. The presence of one O is necessary for electro neutrality. There is no evidence for a preferred position for the one O atom and therefore the refinement was performed with F on all anion sites. Sr7Er6F3oO is paramagnetic and the extrapolation of the magnetic data according to the Curie Weiss law gives 9.5 MB in good agreement with one would expect for Er + with a f 1 configuration. Table 1. Data collection and handling. Crystal: light pink, transparent, irregular, size 0.03 χ 0.03 χ 0.03 mm Wavelength: Ag Ka radiation (0.56066 Â) μ: 196.36 cm 1 Diffractometer, scan mode: Enraf-Nonius CAD4, ω 26max: 59.82° N(hkt)measured, N(hkl)amqae·. 5107,2341 Criterion for /0bs, N(hkl)gc. /obs > 2 a(Us), 1848 N(param)ie fined: 70 Program: SHELXL-97 [4] Table 2. Atomic coordinates and displacement parameters (in Â). Atom Site Occ. X y ζ Un U22 t/33 Ul2 C/13 U23 Er 18/ 0.18466(2) 0.05208(2) 0.17795(2) 0.0142(1) 0.00731(9) 0.00776(9) 0.00543(8) 0.00094(7) 0.00005(7) Sr(l) 3 b 0 0 1/2 0.0144(3) Un 0.0389(8) 0.0072(2) 0 0 Sr(2) 18/ 0.08973(4) 0.32119(4) 0.50514(4) 0.0100(2) 0.0140(2)' 0.0076(1) 0.0083(2) 0.0014(1) 0.0024(1) F(l) 18/ 0.3555(3) 0.1079(3) 0.0913(3) 0.013(1) 0.011(1) 0.010(1) 0.006(1) 0.000(1) -0.002(1) F(2) 18/ 0.1888(3) 0.0529(3) 0.4118(3) 0.022(2) 0.012(1) 0.013(1) 0.007(1) -0.004(1) -0.002(1) F(3) 18/ 0.2680(3) 0.3614(3) 0.4126(3) 0.013(1) 0.011(1) 0.011(1) 0.006(1) -0.001(1) 0.001(1) F(4) 18/ 0.2165(3) 0.1623(3) -0.0021(4) 0.023(2) 0.022(2) 0.016(2) 0.012(2) -0.005(1) 0.005(1) F(5) 18/ 0.2353(4) 0.5293(4) 0.4227(6) 0.022(2) 0.038(3) 0.056(3) 0.023(2) 0.011(2) 0.014(2) F(6) 6c 0.5 0 0 0.075(2) 0.021(4) Un 0.08(1) 0.010(2) 0 0 Unauthenticated Download Date | 3/9/16 10:40 AM