scholarly journals A novel perovskite-like Ta-bronze KTa1+z O3: preparation, stoichiometry, conductivity and crystal structure studies

2001 ◽  
Vol 57 (2) ◽  
pp. 157-162 ◽  
Author(s):  
Alla Arakcheeva ◽  
Gervais Chapuis ◽  
Vladimir Grinevitch ◽  
Vladimir Shamray
Keyword(s):  
Crystal Structure ◽  
Molten Salt ◽  
Molten Salt Electrolysis ◽  
Cubic Crystals ◽  
Space Group ◽  
Temperature Range ◽  
Anisotropic Displacement Parameters ◽  
Atom Position

A new cubic Ta-bronze (1) KTa_{1+z}^{+(5 -\delta)}O3 [z ≃ 0.107 (3)] was obtained on a cathode by molten salt electrolysis of the system K2TaOF5–K3TaO2F4–(KF + NaF + LiF)eutectic. Black, metallic cubic crystals of (1) are formed together with tetragonal β-Ta. The perovskite-like crystal structure of (1) [a = 4.005 (1) Å, space group Pm\bar3m] was refined with anharmonic displacement parameters for Ta and K atoms and anisotropic displacement parameters for a split O-atom position [KM4CCD diffractometer; λ(Mo Kα); 3320 measured reflections with I > 3σ(I); R = 0.0095, wR = 0.0065, Δρmin = −0.91 e Å−3, Δρmax = 0.65 e Å−3]. Defects in the O and K atomic positions were found. (1) is a semiconductor in the temperature range 4–300 K, whereas the well studied and closely related colourless transparent crystals KTa+5O3 (2) are dielectric. Differences in the properties of (1) and (2) are assumed to be connected with the existence of Ta dumb-bells statistically distributed into the KTaO3 matrix.

NQR and Crystal Structure of 4,5-Dichloroimidazole, C3H2N2Cl2

1992 ◽  
Vol 47 (1-2) ◽  
pp. 177-181 ◽  
Author(s):  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Unit Cell ◽  
Space Group ◽  
Temperature Range ◽  
Temperature Coefficients ◽  
Group D

AbstractThe two line 35Cl NQR spectrum of 4,5-dichloroimidazole was measured in the temperature range 77≦ T/K ≦ 389. The temperature dependence of the NQR frequencies conforms with the Bayer model and no phase transition is indicated in the curves v ( 35Cl)= f(T). Also the temperature coefficients of the 35Cl NQR frequencies are "normal". At 77 K the 35Cl NQR frequencies are 37.409 MHz and 36.172 MHz and at 389 K 35.758 MHz and 34.565 MHz. The compound crystallizes at room temperature with the tetragonal space group D44-P41212, Z = 8 molecules per unit cell; at 295 K : a = 684.2(5) pm, c = 2414.0(20) pm. The relations between the crystal structure and the NQR spectrum are discussed.

scholarly journals Synthesis, Crystal Structure and Magnetic Behaviour of Dimeric and Polymeric Gadolinium Trifluoroacetate Complexes

2006 ◽  
Vol 61 (6) ◽  
pp. 699-707 ◽  
Author(s):  
Daniela John ◽  
Alexander Rohde ◽  
Werner Urland
Keyword(s):  
Crystal Structure ◽  
Magnetic Behaviour ◽  
Magnetic Data ◽  
Space Group ◽  
X Ray ◽  
Lattice Constants ◽  
Temperature Range ◽  
X Ray Crystallography ◽  
Carboxylate Groups

The gadolinium(III) trifluoroacetates ((CH3)2NH2)[Gd(CF3COO)4] (1), ((CH3)3NH)[Gd(CF3 COO)4(H2O)] (2), Gd(CF3COO)3(H2O)3 (3) as well as Gd2(CF3COO)6(H2O)2(phen)3 · C2H5OH (4) (phen = 1,10-phenanthroline) were synthesized and structurally characterized by X-ray crystallography. These compounds crystallize in the space group P1̅ (No. 2, Z = 2) (1, 2 and 4) and P 21/c (No. 14, Z = 4) (3), respectively, with the following lattice constants 1: a = 884.9(2), b = 1024.9(2), c = 1173.1(2) pm, α = 105.77(2), β = 99.51(2), γ = 107.93(2)°; 2: a = 965.1(1), b = 1028.6(1), c = 1271.3(2) pm, α = 111.83(2), β = 111.33(2), γ = 90.44(2)°; 3: a = 919.6(2), b = 1890.6(4), c = 978.7(2) pm, β = 113.94(2)°; 4: a = 1286.7(8), b = 1639.3(8), c = 1712.2(9) pm, α = 62.57(6), β = 84.13(5), γ = 68.28(5)°. The compounds consist of Gd3+ ions which are bridged by carboxylate groups either to chains (1 and 2) or to dimers (3 and 4). In addition to the Gd3+ dimers, compound (4) also contains monomeric Gd3+ units. The magnetic behaviour of 2 and 3 was investigated in a temperature range of 1.77 to 300 K. The magnetic data for these compounds indicate weak antiferromagnetic interactions

79Br, 127I NQR of Diammoniumalkyl Halides and Piperazinium Halides. Crystal Structure of Piperazinium Dibromide Monohydrate and Piperazinium Monoiodide

1989 ◽  
Vol 44 (1) ◽  
pp. 41-55 ◽  
Author(s):  
Jutta Hartmann ◽  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Temperature Range

Abstract The 79Br and 127I NQR spectra were investigated for 1,2-diammoniumethane dibromide, -diiodide, 1,3-diammoniumpropane dibromide, -diiodide, piperazinium dibromide monohydrate, and piperazinium monoiodide in the temperature range 77 ≦ T/K ≦ 420. Phase transitions could be observed for the three iodides. The temperatures for the phase transitions are: 400 K and 404 K for 1,2-diammoniumethane diiodide, 366 K for 1,3-diammoniumpropane diiodide, and 196 K for piperazinium monoiodide.The crystal structures were determined for the piperazinium compounds. Piperazinium dibromide monohydrate crystallizes monoclinic, space group C2/c, with a= 1148.7 pm, 0 = 590.5 pm, c= 1501.6pm, β = 118.18°, and Z = 4. For piperazinium monoiodide the orthorhombic space group Pmn 21 was found with a = 958.1 pm, b = 776.9 pm, c = 989.3 pm, Z = 4. Hydrogen bonds N - H ... X with X = Br, I were compared with literature data.

Preliminary Studies of the Obtaining of Solid Metallic Cerium from Fluoride Melts

2003 ◽  
Vol 58 (1) ◽  
pp. 57-62 ◽  
Author(s):  
Virgil Constantin ◽  
Ana-Maria Popescu ◽  
Stefania Zuca
Keyword(s):  
Current Efficiency ◽  
Molten Salt ◽  
Molten Salt Electrolysis ◽  
Temperature Range ◽  
Cubic Form ◽  
Fluoride Melts ◽  
Molten Electrolyte ◽  
A Current ◽  
Decomposition Potential

The present study deals with the obtaining of solid cerium by molten salt electrolysis of a 46.74 - 48.26 - 5wt% LiF-NaF-NaCeF4 mixture, in the temperature range 700 - 730 °C and with a current efficiency of ~ 75%. For this purpose NaCeF4 was obtained, characterized and it’s cubic form was identified. The solubility and decomposition potential of this compound in the molten electrolyte 49.2 - 50.8% LiF-NaF was also studied.

The Crystal Structure of [Bis(tri-tbutyl-phosphine)gold(I)] Chloride

1994 ◽  
Vol 49 (9) ◽  
pp. 1243-1246 ◽  
Author(s):  
Edgar Zeller ◽  
Annette Schier ◽  
Hubert Schmidbaur
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Chloride Complexes ◽  
Cubic Crystals ◽  
Space Group

The title compound is available from the reaction of labile gold(I) chloride complexes and an excess of the ligand (tBu3P), or from the NaBH4 reduction of (tBu3P)AuCl. It forms dark red cubic crystals, [a = 14.297(1) Å at -56 °C, space group P213, Z = 4], with isolated chloride anions and [(tBu3P)2Au]+ cations of C3 symmetry, with linear two-coordinate gold centers

Crystal structure and thermal expansion of hexakis(phenylthio)benzene and its CBr4 clathrate

1995 ◽  
Vol 73 (4) ◽  
pp. 513-521 ◽  
Author(s):  
Darek Michalski ◽  
Mary Anne White ◽  
Pradip K. Bakshi ◽  
T. Stanley Cameron ◽  
Ian Swainson
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
Neutron Powder Diffraction ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

The crystal structures of hexakis(phenylthio)benzene (HPTB) and its CBr4 clathrate have been determined by single crystal X-ray diffraction data collected at T = 18 °C and refined to final Rw of 0.036 and 0.047, respectively. Pure HPTB is triclinic, space group [Formula: see text] (No. 2), with a = 9.589(2) Å, b = 10.256(1) Å, c = 10.645(2) Å, α = 68.42(1)°, β = 76.92(2)°, γ = 65.52(1)°, and Z = 1. The CBr4 clathrate of HPTB is rhombohedral, space group [Formula: see text] (No. 148), with a = 14.327(4) Å, b = 20.666(8) Å, and Z = 3. The host–guest mole ratio of HPTB–CBr4 is 1:2. Neutron powder diffraction was carried out on powders of both compounds in the temperature range 25 K < T < 295 K. Thermal expansion coefficients were determined for HPTB and HPTB–CBr4 over this temperature range. Keywords: thermal expansion, crystal structure, clathrate.

Halogen NQR and Crystal Structure of Ammonium Halides (R-NH3)+X- and (X–) (+H3NR´­NH3+) (X–). R = (HOCH2)3C, R´ = CH2C(CH3)2CH2; X = I,Br

1994 ◽  
Vol 49 (1-2) ◽  
pp. 174-184
Author(s):  
Shi-qi Dou ◽  
Hartmut Fuess ◽  
Helmut Paulus ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Unit Cell ◽  
Space Group ◽  
Temperature Range ◽  
Ammonium Halides

AbstractThe 127I-NQR of(HOCH2)3CNH3+ I- was determined in the range 77 ≤ T/K ≤ 310. At T = 310 K the NQR signal fades out (Tm = 463 K). The 127I spectrum ( T =77 K.): v1 =29.195 MHz, v2 = 14.597 MHz, η(121l)=0, e QΦzz h-1 (127I) = 97.315 MHz, is in agreement with the crystal structure. The 127I NQR spectrum of 1,3-diammonium-2,2-dimethylpropane diiodide, (H3NCH2C(CH3)2CH2NH3)2+ ·2I- , is a quartet within the whole temperature range investigated, and the lines correspond to two crystallographically independent iodines: Space group P21/c, Z = 4, a = 731.2(3) pm, b = 689.0(3) pm, c = 2255.1(8) pm, β = 104.90(1)°. At 7 = 7 7 K the 127I NQR quartet is (MHz): v1 = 34.145, v2 = 32.805, v3 = 22.113, v4 = 16.787; at 295 K (same order, MHz): 30.559, 29.729, 19.810, 15.651. There are two combinations of the NQR frequencies. Considering the coordination of I-, the hydrogen bonds N -H ··· I, eQΦzzQ h-1 and η, we choose for I(1) v1 and v3, for I(2) v2 and v4. At 77 K eQΦzzQ h-1 (I(1))= 118.86 MHz,η (127I(1)) = 0.498, eQΦzzQ h-1 (I(2)) = 109.75 MHz, η(127I(2)) = 0.135 follow for the two iodine atoms. Both, eQΦzzQ h-1 (I(1)) and e eΦzzQ h-1(I(2)) decrease smoothly with increasing T: η I(2)) increases with increasing T whereas η(127I(1)) is almost constant within 77 ≤ T /K ≤ 4 0 6 . The 79,81Br NQR spectrum of l,3-diamino-2,2-dimethylpropane dihydrobromide is also a quartet, showing two crystallographic inequivalent Br atoms in the unit cell. The frequencies are (T =273 K, MHz): v1 (79Br)= 14.303, v2 (79Br)= 12.884, (81Br)= 11.951, v2(81Br) = 10.781; space group C2/c, Z = 8 , a = 2136.4(6) pm, b = 854.6(3) pm, c = 1125.8(3) pm, β = 93.23(1)°. Crystal structures and NQR results are discussed.

scholarly journals Redetermination of ruizite, Ca2Mn3+2[Si4O11(OH)2](OH)2·2H2O

2016 ◽  
Vol 72 (7) ◽  
pp. 959-963 ◽  
Author(s):  
Kim V. Fendrich ◽  
Robert T. Downs ◽  
Marcus J. Origlieri
Keyword(s):  
Crystal Structure ◽  
South Africa ◽  
Natural Sample ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
Space Group ◽  
X Ray ◽  
Isotropic Displacement Parameter ◽  
Northern Cape ◽  
Anisotropic Displacement Parameters

The crystal structure of ruizite, ideally Ca2Mn3+2[Si4O11(OH)2](OH)2·2H2O [dicalcium dimanganese(III) tetrasilicate tetrahydroxide dihydrate] was first determined in space groupA2 with an isotropic displacement parameter model (R= 5.6%) [Hawthorne (1984).Tschermaks Mineral. Petrogr. Mitt.33, 135–146]. A subsequent refinement in space groupC2/mwith anisotropic displacement parameters for non-H atoms converged withR= 8.4% [Mooreet al.(1985).Am. Mineral.70, 171–181]. The current study reports a redetermination of the ruizite structure by means of single-crystal X-ray diffraction data of a natural sample from the Wessels mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Our data (R1= 3.0%) confirm that the space group of ruizite is that of the first study rather thanC2/m. This work improves upon the structure reported by Hawthorne (1984) in that all non-H atoms were refined with anisotropic displacement parameters and all hydrogen atoms were located. The crystal structure consists of [010] chains of edge-sharing MnO6octahedra flanked by finite [Si4O11(OH)2] chains. The Ca2+cations are situated in the cavities of this arrangement and exhibit a coordination number of seven.

scholarly journals Kristallstruktur- und MoBbauer-Untersuchungen am Lithiumhexacyanoferrat(III)-Hexamethylentetramin-Addukt Li3[Fe(CN)6] ·2C6H12N4 · 5H20 / Crystal Structure and Mossbauer Studies of the Lithium Hexacyanoferrate(III)-Hexamethylenetetramine Adduct Li3[Fe(CN)6] · 2C6H12N4 · 5H2O

1984 ◽  
Vol 39 (9) ◽  
pp. 1162-1166 ◽  
Author(s):  
Joachim Pickardt ◽  
Jorg Kahler ◽  
Norbert Rautenberg ◽  
Erwin Riedel
Keyword(s):  
Crystal Structure ◽  
Mössbauer Spectra ◽  
Statistical Distribution ◽  
Water Molecules ◽  
Orthorhombic Space Group ◽  
Lithium Ions ◽  
Space Group ◽  
Mössbauer Studies ◽  
Temperature Range ◽  
Mossbauer Spectra

Crystals of the adduct Li3[Fe(CN)6] · 2C6H12N4-5H2O are orthorhombic, space group I2mm, Z = 2, a = 909.4(5), b = 1046.1(5), c = 1455.8(5) pm. The structure may be regarded as a packing of Fe(CN)6 octahedra and hexamethylenetetramine molecules. The lithium ions are coordinated to nitrogen atoms of both groups and to water molecules. Mossbauer spectra have been recorded for the temperature range between 290 K and 77 K. At all temperatures the spectra show two doublets with nearly identical isomer shifts but different quadrupole splittings, thus indicating the presence of two kinds of hexacyanoferrate(III) ions with slightly different distortions of the ligand spheres around the Fe atoms. The effect is discussed on the assumption of a statistical distribution of one of the lithium ions.

Synthese und Kristallstruktur von Te42+(WCl6-)2 / Synthesis and Crystal Structure of Te42+(WCl6-)2

1990 ◽  
Vol 45 (4) ◽  
pp. 413-416 ◽  
Author(s):  
Johannes Beck
Keyword(s):  
Crystal Structure ◽  
Bond Length ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
Moist Air ◽  
Triclinic Space Group ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
Lattice Constants ◽  
Temperature Range

WCl6 reacts with two equivalents of tellurium in a sealed evacuated ampoule in the temperature range from 170 to 190 °C to give Te42+(WCl6-)2. Under the same conditions with one equivalent of tellurium WCl5 yields Te42+(WCl6-)2 and WCl4. Te4(WCl6), formes black crystals, which are sensitive to moist air. It decomposes at temperatures above 300° C to Te and WCl6. The crystal structure determination (lattice constants a = 638.9(1), b = 753.2(2), c = 1102.0(5) pm, α = 101.19(2)°, β = 102.85(2)°, γ = 90.21(1)°, Z = 1, triclinic space group P 1̄, 3572 unique reflections for 82 parameters, final R = 0.026) shows the nearly ideal square Te42+ cation with Te–Te distances of 268.8 and 268.7 pm and markedly distorted WCl6– octaedra with W–Cl bond length from 227.5 to 237.3 pm. The structure involves interionic Te–Cl contacts as short as 319 pm.

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