| | 1 | Author
| Ratikanta Mishra, Rolf-Dieter Hoffmann, Rainer Pöttgen | Requires cookie* | | | Title
| New Magnesium Compounds /fcE2Cu2Mg (RE = Y, La -Nd, Sm, Gd -Tm, Lu) with Mo2FeB2 Type Structure  | | | | Abstract
| The title compounds were synthesized by reaction of the elements in sealed tantalum tubes in a water-cooled sample chamber in a high-frequency furnace. These magnesium intermetallics crystallize with the tetragonal Mo2FeB2 type structure, space group PMmbm. The lattice pa rameters of all compounds were refined from X-ray powder data. Single crystal X-ray data yielded a = 792.09(6), c = 396.31(8) pm, wR2 = 0.0396, 315 F 2 values for La2Cu2Mg, a = 778.30(5), c = 384.04(5) pm, wR2 = 0.0954, 214 F 2 values for Nd2Cu2Mg, and a = 762.65(5), c = 374.09(3) pm, wR2 = 0.0566, 186 F 2 values for Y2Cu2Mg with 12 variable parameters for each refinement. The /?£, 2Cu2Mg structures can be described as an intergrowth of distorted A1B2 and CsCl related slabs of compositions RECui and REMg. Chemical bonding in La2Cu2Mg was investigated on the basis of extended Hückel calculations and compared to isotypic La2Cu2ln. This structure was also refined from single crystal X-ray data: PMmbm, a = 780.8(2), c = 400.1(2) pm, wR2 = 0.0351, 211 F 2 values and 12 variable parameters. | | | |
Reference
| Z. Naturforsch. 56b, 239—244 (2001); received January 25 2001 | | | |
Published
| 2001 | | | |
Keywords
| Intermetallic Compounds, Magnesium, Crystal Structure | | | |
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| default:Reihe_B/56/ZNB-2001-56b-0239.pdf | | | | Identifier
| ZNB-2001-56b-0239 | | | | Volume
| 56 | |
| 3 | Author
| H. P. Fritz | Requires cookie* | | | Title
| The Stannides RE R hSn (RE = Ho -Yb) and ScTSn (T = Pd, Pt) -Structure Refinements and 119Sn Mössbauer Spectroscopy | | | | Abstract
| The stannides RERhSn (RE = Ho -Yb) and ScTSn (T = Pd, Pt) were prepared by reaction of the elements in sealed tantalum tubes in a high-frequency furnace, by arc-melting, or by a tin-flux technique in quartz tubes. The rhodium based stannides crystallize with the ZrNiAl type structure, space group P62m. The four structures were refined from single crystal X-ray data: a = 754.5(3), c = 377.1(1) pm, wR2 = 0.0357, 233 F 2 values for HoRhSn, a = 753.3(1), c = 372.16(8) pm, wR2 = 0.0721, 233 F 2 values for ErRhSn, a = 753.7(3), c = 369.0(2) pm, wR2 = 0.0671,233 F 2 values for TmRhSn, and a = 753.17(5), c = 366.53(4) pm, wR2 = 0.0566, 180 F 2 values for YbRhSn with 14 parameters for each refinement. ScPdSn and ScPtSn adopt the HfRhSn type, a superstructure of ZrNiAl, space group P62c: a = 747.5(1), c = 710.2(1) pm, for ScPdSn, and a = 738.37(9), c = 729.47(9) pm, wR2 = 0.0452,369 F 2 values, 18 variables for ScPtSn. Structural motifs in these stannides are transition metal centered trigonal prisms formed by the rare earth and tin atoms. While these prisms are regular in the rhodium based stannides, significant distortions occur in ScPdSn and ScPtSn. The formation of the superstructure can be ascribed to packing reasons. The shortest interatomic distances occur between the transition metal (T) and tin atoms. These atoms form three-dimensional [FSn] networks in which the rare earth atoms fill distorted hexagonal channels. The series RERhSn displays a somewhat unique behavior. The a lattice parameter is more or less independent of the rare earth element, while the c lattice parameter shows the expected lanthanoid contraction. ll9Sn Mössbauer spectroscopic data of the rhodium stannides show signals at isomer shifts varying from 1.77 to 1.82 mm/s subject to quadrupole splitting between 0.75 to 0.82 mm/s. | | | |
Reference
| Z. Naturforsch. 56b, 589—597 (2001); received April 12 2001 | | | |
Published
| 2001 | | | |
Keywords
| Stannides, Crystal Structure, Mössbauer Spectroscopy | | | |
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| default:Reihe_B/56/ZNB-2001-56b-0589.pdf | | | | Identifier
| ZNB-2001-56b-0589 | | | | Volume
| 56 | |
| 4 | Author
| Thom As Fickenscher, G. Unter Kotzyba, Rolf-D Ieter, H. Offm, Ann, R. Ainer Pöttgen, H. P. Fritz | Requires cookie* | | | Title
| Synthesis, Structure, and Magnetic Properties of EuAgCd and YbAgCd | | | | Abstract
| New intermetallic compounds EuAgCd and YbAgCd were synthesized in quantitative yield by reaction of the elements in sealed tantalum tubes in a high-frequency furnace. Both com pounds were investigated by X-ray diffraction on powders and single crystals: KHg2 type, Imma, a = 490.41(8), b = 771.0(1), c = 834.4(2) pm, wR2 = 0.0624, 255 F values, 12 variables for EuAgCd, and MgZn2 type, Pb^/mmc, a = 584.66(5), c = 946.83(9) pm, wR2 = 0.0502, 187 F 2 values, 11 variables for YbAgCd. Owing to the very small difference in scattering power, no long range ordering of the silver and cadmium atoms is evident from the X-ray data, although Ag-Cd ordering is expected. The silver and cadmium atoms randomly occupy the mercury and zinc positions of the KHg2 and MgZn2 type structures, respectively. In EuAgCd the [AgCd] substructure consists of strongly puckered, orthorhombically distorted Ag3 Cd3 hexagons, while a three-dimensional network of face-and comer-sharing tetrahedra is observed in YbAgCd. The rare earth atoms fill the space between the Ag3 Cd3 hexagons (EuAgCd) or within the three-dimensional tetrahedral network (YbAgCd). Magnetic susceptibility measurements in dicate Pauli paramagnetism for YbAgCd and Curie-Weiss behavior above 60 K for EuAgCd with an experimental magnetic moment of 7.82(3) /j b/Eu indicating divalent ytterbium and europium. Ferromagnetic ordering at Tc = 28.0(5) K is observed for EuAgCd. At 2 K and 5 T the saturation magnetization is 5.85(5) /iß/Eu. | | | |
Reference
| Z. Naturforsch. 56b, 598—603 (2001); received April 12 2001 | | | |
Published
| 2001 | | | |
Keywords
| Cadmium, Crystal Structure, Magnetic Properties | | | |
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| default:Reihe_B/56/ZNB-2001-56b-0598.pdf | | | | Identifier
| ZNB-2001-56b-0598 | | | | Volume
| 56 | |
| 5 | Author
| Hans Bock, Erik Heigel, Zdenek Havlas3 | Requires cookie* | | | Title
| Wechselwirkungen in Molekülkristallen, 175 [1, 2]. Kristallzüchtung und Strukturbestimmung von {Cäsium-tetraphenylimido- diphosphatj-Aggregaten mit unterschiedlicher lipophiler Umhüllung durch verschiedenartig Methyl-substituierte Phenylringe sowie relativistische DFT-Modellberechnungen zu Cäsium/Cäsium-Wechselwirkungen Interaction in M olecular Crystals, 175 [1,2]. Crystal Growth and Structure Determination of {Cesium-tetraphenylimidodiphosphate} Aggregates with Differing Lipophilic Wrapping Due to Differently Methyl-Substituted Phenyl Rings, and Relativistic DFT-Model Calculations of Cesium/Cesium Interactions | | | | Abstract
| In alkali-tetraphenylimidodiphosphate ion aggregates, the size of the cation determines the curvature of the ligand and, therefore, whether hexameric ellipsoidal clusters or polymeric chains are formed. To further characterize the ligand spatial requirements, the phenyl rings have been methylsubstituted in 4-, 3/5-, 3/4-or 2,3-positions, their conformations structurally analyzed and correlated with the van der Waals substituent profiles. In addition, relativistic density functional theory potential curves have been calculated for the Cs0 --Cs® interactions in simplified model systems. | | | |
Reference
| Z. Naturforsch. 56b, 483—511 (2001); eingegangen am 21. Dezember 2000 | | | |
Published
| 2001 | | | |
Keywords
| Cesium Tetraphenylimidodiphosphates, Methyl Substitution Effects, Polyion Aggregates, Crystal Structures | | | |
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| default:Reihe_B/56/ZNB-2001-56b-0483.pdf | | | | Identifier
| ZNB-2001-56b-0483 | | | | Volume
| 56 | |
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