Crystal structure of neodymium palladium antimonide, NdPd0.85Sb2

Abstract

NdPd0.85Sb2, tetragonal, P4/nmm (no. 129), a = 4.4098(3) A, c = 9.6907(9) A,V = 188.4 A , Z = 2,Rg t(F) = 0.0369, wRref(F) = 0.0383, T = 295 K. Source of material Apolycrystalline sample with the nominal compositionNdPdSb2 was prepared fromNd (99,99%), Pd (99,99%) and Sb (99,99%) ingots. The components were mixed in a ratio of Nd:Pd:Sb = 1:1:2with an excess of 2 at.%of Sb, because of the relatively high vapor pressure of Sb and pressed into a pellet. Then the sample was repeatedly melted in an arc-furnace under purified argon atmosphere to achieve homogeneity. Afterwards it was heated in a fused quarz glass tube under vacuum at 600 oC for 750 h, quenchedwith coldwater. The air-stable samplewas crushed and single crystals with a prismatic formand ametallic luster were selected for a single crystal structure determination. Experimental details The composition of the sample was checked using energydispersive X-ray spectroscopy (TESCAN 5130MM scanning electronmicroscopewithOxford Si-detector) and resulted in a ratio ofNd:Pd:Sb = 25.4:21.5:53.1 (standard deviation estimated to be about 1.5 at.%). No impurities were detected. Discussion The structure of the ternary antimonide NdPd0.85Sb2 [1, 2] belongs to the HfCuSi2 type structure which is closely related to the structure type ofBaAl4 [3]. In the structure ofNdPd0.85Sb2 the two crystallographically different Sb atoms and the Nd atoms fully occupy the positions 2a and 2c, respectively,whereas the position 2b is only 85 % occupied by Pd atoms. The structure of NdPd0.85Sb2 can be described in terms of double layers of corner sharing [Sb(2)Pd4/4Nd4/4] square antiprisms separated by flat nets of Sb1 atoms. Within these nets the Sb1 atoms are square planar coordinated by 4 Sb1 with distances of 311 pm indicating Sb–Sb bonding interactions. In contrast the Sb2 atoms exhibit Sb–Sb distances larger than 400 pm and can therefore be considered as discrete. The Pd–Sb and Nd–Sb distances in the structure of NdPd0.85Sb2 are in good agreement with the sum of the adjacent atomic radii (rNd = 0,1814 nm, rPd = 0,1376 nm, rSb = 0,141 nm [4]). Z. Kristallogr. NCS 227 (2012) 287-288 / DOI 10.1524/ncrs.2012.0189 287 © by Oldenbourg Wissenschaftsverlag, Munchen Crystal: metallic, prism-like, size 0.0223(0.0259(0.0712 mm Wavelength: Mo K3 radiation (0.71073 A) %: 311.6 cm Diffractometer, scan mode: Mercury70 CCD, 2(2 bin 27max: 144.4° N(hkl)measured, N(hkl)unique: 821, 821 Criterion for Iobs, N(hkl)gt: Iobs > 4 $(Iobs), 204 N(param)refined: 7 Programs: WINCSD [5] Table 1. Data collection and handling. _____________ * Correspondence author (e-mail: J.Koehler@fkf.mpg.de) Unauthenticated Download Date | 3/9/16 11:11 AM Nd 2c 1⁄4 1⁄4 0.7544(3) 0.65(5) 0.65(5) 0.68(8) 0 0 0 Pd 2a 0.85(1) 3⁄4 1⁄4 0 0.64(9) 0.64(9) 0.84(11) 0 0 0 Sb1 2b 3⁄4 1⁄4 1⁄2 0.50(7) 0.50(7) 1.13(9) 0 0 0 Sb2 2c 1⁄4 1⁄4 0.1507(4) 0.96(7) 0.96(7) 1.40(11) 0 0 0 Table 2. Atomic coordinates and displacement parameters (in A). Atom Site Occ. x y z B11 B22 B33 B12 B13 B23 288 NdPd0.85Sb2 Acknowledgments. The authors thank H. Gartling (Max-Planck-Institute for Solid State Research, Stuttgart, Germany) for the single crystal data collection.