Die Kristallstrukturen von Verbindungen des Typs A2TeX6 (A = K, NH4, Rb, Cs; X = Cl, Br, I) / The Crystal Structures of Compounds A2TeX6 (A = K, NH4, Rb, Cs; X = Cl, Br, I)

1989 ◽  
Vol 44 (10) ◽  
pp. 1187-1194 ◽  
Author(s):  
Walter Abriel ◽  
André du Bois
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Crystal Structures ◽  
Soft Mode ◽  
Type Structure ◽  
Ionic Radii ◽  
Space Group ◽  
Space Groups ◽  
Structure Space

With the determination of the crystal structure of (NH4)2TeI6 the list of the descriptions of A2TeX6 structures is further completed. At 293 K three structure types are observed with an antifluorite packing of cations and anions: The cubic K2PtCl6 type structure (space group Fm 3̄ m, Z = 4), the tetragonal Rb2TeI6 type structure (space group P4/mnc, Z = 2), and the monoclinic K2TeBr6 type structure (space group P21/n, Z = 2). The latter type was found for (NH4)2TeI6 with a = 8.0694(7), b = 8.0926(9), c = 11.7498(8) Å and β = 89.605(8)° and refined to a final Rw of 0.065. From ionic radii ratios the symmetry of the A2MX6 type structures can be predicted including a prediction of low temperature instability (soft mode condensation). Group-subgroup relationships connect the corresponding space groups and the space groups of the high/low temperature polymorphs.

Studies on some MG6 · LR6 compounds. II. Crystal structure of zinc fluotitanate hexahydrate and its low temperature phase

1996 ◽  
Vol 211 (6) ◽  
Author(s):  
G. Mostafa ◽  
S. Ray ◽  
A. Mukhopadhyay
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Thermal Parameter ◽  
Temperature Phase ◽  
Space Group ◽  
Structure Space ◽  
Low Temperature Phase

AbstractA previous determination of the structure of zinc fluotitanate hexahydrate was considered unsatisfactory because an abnormal anisotropic thermal parameter was attributed to the F atom. The structure (space group

scholarly journals New Compounds RE(Zn,Al)8 and Yb4Zn20.3Al12.7 and their Crystal Structures

2006 ◽  
Vol 61 (7) ◽  
pp. 779-784 ◽  
Author(s):  
Ol’ga Stel’makhovych ◽  
Yurij Kuz’ma
Keyword(s):  
Intermetallic Compound ◽  
Crystal Structures ◽  
Structure Type ◽  
Type Structure ◽  
Space Group ◽  
X Ray ◽  
Structure Space ◽  
New Compounds ◽  
First Time ◽  
The Relationship

The crystal structures of several new compounds have been determined using X-ray analysis. The intermetallic compound HoZn5Al3 (a = 8.586(3), c = 16.538(5) Å , RF = 0.0413, RW = 0.0521) has its own structure type (space group I4/mmm), which has been found for the first time. The following compounds are isostructural with the previous one: YZn5.52Al2.48 (a = 8.6183(1), c = 16.5048(3) Å , RI = 0.078, RP = 0.116), DyZn4.96Al3.04 (a = 8.5887(1), c = 16.5002(3) Å , RI = 0.077, RP = 0.114), ErZn5.37Al2.63 (a = 8.5525(2), c =16.3997(5) Å , RI = 0.081, RP = 0.111), TmZn5.64Al2.36 (a = 8.70429(8), c = 16.3943(4) Å , RI = 0.088, RP = 0.095), LuZn5.58Al2.42 (a = 8.5616(1), c= 16.3052(3) Å , RI =0.081, RP =0.101). The intermetallic compound Yb4Zn20.3Al12.7 (a = 8.6183(1), c = 16.5048(3) Å , RI = 0.085, RP = 0.112) adopts the Yb8Cu17Al49 - type structure (space group I4/mmm). The relationship between the HoZn5Al3-type and the Yb8Cu17Al49-type structures is discussed.

scholarly journals Darstellung und Struktur ternärer Silizide und Germanide des Lithiums mit den Seltenen Erden Y und Gd im Fe2P-Typ / Preparation and Crystal Structure of Ternary Silicides and Germanides of Lithium with the Rare-Earth-Metals Y and Gd in the Fe2P-Type Structure

1979 ◽  
Vol 34 (8) ◽  
pp. 1057-1058 ◽  
Author(s):  
Axel Czybulka ◽  
Günter Steinberg ◽  
Hans-Uwe Schuster
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Crystal Structures ◽  
Rare Earth Metals ◽  
Type Structure ◽  
Space Group ◽  
X Ray ◽  
P Type ◽  
Type Lattice ◽  
The Rare Earth

In the systems Li-M-X = (M = Y, Gd; X = Si, Ge) the compounds LiYSi, LiYGe and LiGdGe were prepared. Their crystal structures were determined by X-ray investigations. They crystallize hexagonally (space group P 6̄2m), and a C22-(Fe2P-type) lattice was found

Aragonite-type lanthanum orthoborate, LaBO3

2006 ◽  
Vol 62 (4) ◽  
pp. i103-i105 ◽  
Author(s):  
Akihiko Nakatsuka ◽  
Osamu Ohtaka ◽  
Hiroshi Arima ◽  
Noriaki Nakayama ◽  
Tadato Mizota
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Single Crystal ◽  
General Position ◽  
Type Structure ◽  
Space Group ◽  
X Ray ◽  
Thermal Vibrations

The crystal structure of the low-temperature (LT) modification of LaBO3 has been redetermined from single-crystal X-ray data; the resulting structure confirms the previous study [Abdullaev, Dzhafarov & Mamedov (1976). Azerbaidzhanskii Khim. Zh. pp. 117–120], but with improved precision. LT-LaBO3 crystallizes in space group Pnma and adopts the aragonite-type structure. Except for one O atom, which is situated on a general position, all other atoms (one La, one B and a second O atom) lie on mirror planes. The structure is composed of LaO9 polyhedra with an average La—O distance of 2.593 Å and trigonal BO3 groups with an average B—O distance of 1.373 Å. Slight anisotropies of the thermal vibrations of La and B atoms suggest that the electrostatic La...La and La...B interactions across the shared edges are weak.

Synthese und Kristallstrukturen von N-[ω-(Dimethylammonio)alkyl]- N´,N´,N´´,N´´-tetramethylguanidinium-chlorid-tetraphenylboraten / Synthesis and Crystal Structures of N-[ω-(Dimethylammonio)alkyl]-N´,N´,N´´,N´´- tetramethylguanidinium Chloride Tetraphenylborates

2010 ◽  
Vol 65 (7) ◽  
pp. 907-916 ◽  
Author(s):  
Ioannis Tiritiris ◽  
Falk Lissner ◽  
Thomas Schleid ◽  
Willi Kantlehner
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Room Temperature ◽  
Chloride Ions ◽  
Monoclinic Space Group ◽  
Temperature Structure ◽  
Space Group ◽  
Temperature Modification

Dicationic N,N´,N´,N´´,N´´-pentasubstituted guanidinium dichlorides 4a, b are obtained from the chloroformamidinium salt 2 and diamines 3a, b. N-[2-(Dimethylammonio)ethyl]-N´,N´,N´´,N´´-tetramethylguanidinium chloride tetraphenylborate (5a) and N-[3-(dimethylammonio)propyl]-N´,N´,N´´,N´´-tetramethylguanidinium chloride tetraphenylborate (5b) were synthesized from 4a, b by anion metathesis with one equivalent of sodium tetraphenylborate. The thermal properties of the salts 5a, b were studied by means of DSC methods, and their crystal structures were determined by single-crystal X-ray diffraction analysis. For 5a a solid-solid phase transition is observed at −156 ◦C to a low-temperature structure. The room-temperature modification (α-5a) crystallizes in the centrosymmetric orthorhombic space group Pbca (a = 13.1844(4), b = 13.8007(4), c = 34.7537(11) A° ).The guanidinium ions are interconnected via chloride ions through bridging N-H· · ·Cl hydrogen bonds, providing isolated units. The tetraphenylborate ions show some dynamic disordering in the crystal structure. The low-temperature modification (β -5a) also crystallizes orthorhombically, but in the non-centrosymmetric space group Pna21 (a = 13.1099(4), b = 69.1810(11), c = 13.5847(5) A° ) and consists of four crystallographically independent cations and anions in the unit cell. Compared with the room-temperature structure, a similar N-H· · ·Cl hydrogen bond pattern is observed in the β -phase, but the tetraphenylborate ions are now completely ordered. 5b crystallizes in the monoclinic space group P21/c (a = 10.8010(3), b = 14.1502(5), c = 20.9867(9) A° , β = 94.322(1)◦). In the crystal structure the guanidinium ions are linked via chloride ions through N-H· · ·Cl hydrogen bonds, but in contrast to 5a two infinite strands are formed along the a axis with the tetraphenylborate ions interspersed between them for charge compensation.

AB2X2-Verbindungen im CaAl2Si2-Typ, V[1] Zur Struktur der Verbindungen CaMn2P2, CaMn2As2, SrMn2P2 und SrMn2As2 / AB2X2-Compounds with the CaAl2Si2 Structure, V [1] The Crystal Structure of CaMn2P2, CaMn2As2, SrMn2P2, and SrMn2As2

1978 ◽  
Vol 33 (6) ◽  
pp. 606-609 ◽  
Author(s):  
Albrecht Mewis
Keyword(s):  
Crystal Structure ◽  
Type Structure ◽  
Space Group ◽  
X Ray ◽  
Lattice Constants ◽  
Ternary Compounds ◽  
Structure Space ◽  
Ray Methods

Abstract Four ternary compounds with the formulas CaMn2P2, CaMn2As2, SrMn2P2, and SrMn2As2 have been prepared and investigated by X-ray methods. They are isotypic and crystallize trigonally in a CaAl2Si2-type structure (space group P3̅m 1-D33d) with the lattice constants: CaMn2P2 a = 4,096 ± 0,001 Å, c = 6,848 ± 0,002 Å, CaMn2As2 a = 4,239 ± 0,001 Å, c = 7,027 ± 0,003 Å, SrMn2P2 a = 4,168 ± 0,001 Å, c = 7,132 ± 0,001 Å, SrMn2As2 a = 4,306 ± 0,001 Å, c = 7,315 ± 0,001 Å. The lattice constants of BaMn2P2 and BaMn2As2 are given

Über Oxoplumbate(IV) Die Kristallstruktur von HT-Li2PbO3 [1] The Crystal Structure of HT-Li2PbO3 [1] / On Oxoplumbates(IV) The Crystal Structure of HT-Li2PbO3 [1]

1983 ◽  
Vol 38 (6) ◽  
pp. 661-664 ◽  
Author(s):  
Berthold Brazel ◽  
Rudolf Hoppe
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Structure Determination ◽  
Type Structure ◽  
Ionic Radii ◽  
Space Group ◽  
Coordination Numbers

Abstract Single crystals of HT-Li2PbO3 have been prepared by heating of mixtures of Rb2PbO3 and Li2O [Ag-cylinders, 600 °C, 100 d]. The structure determination [1005 symmetry independent l0(hkl), R = 5.85%, Rw = 5.35%, confirms space group C2/c with a = 548.60(16), b = 949.51(22), c = 1027.35(27) pm, β = 100.11(3)°, drö = 6.78 g · cm-3 , dpyk = 6.80 g · cm-3 , Z - 8. The NaCl-type structure variant is characterized by alter-nating layers of Li+ and Pb4+ /Li+ cations, which are all octahedrally coordinated. Effective Coordination Numbers, ECoN are calculated via Mean Fictive Ionic Radii, MEFIR.

Zur Kristallstruktur von Ho2Se3/ On the Crystal Structure of Ho2Se3

1998 ◽  
Vol 53 (8) ◽  
pp. 900-902 ◽  
Author(s):  
Werner Urland ◽  
Helmut Person
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Chemical Transport ◽  
Type Structure ◽  
Space Group ◽  
Lattice Constants ◽  
Brownish Yellow ◽  
Structure Space

Abstract Starting from HoSe2-x powder and holmium metal bright brownish-yellow, plate-like single crystals of Ho2Se3 could be prepared by chemical transport with AlCl3. Holmium sesquiselenide crystallizes in the Sc2S3-type structure, space group Fddd, with lattice constants a = 1140,7(2), b -812,6(1) and c = 2423,9(3) pm.

Determination of the structure of the violet pigment C22H12Cl2N6O4 from a non-indexed X-ray powder diagram

2005 ◽  
Vol 61 (1) ◽  
pp. 37-45 ◽  
Author(s):  
Martin U. Schmidt ◽  
Martin Ermrich ◽  
Robert E. Dinnebier
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Lattice Energy ◽  
Frankfurt Am Main ◽  
Rietveld Refinements ◽  
X Ray ◽  
Space Groups ◽  
Violet Pigment

The violet pigment methylbenzimidazolonodioxazine, C22H12Cl2N6O4 (systematic name: 6,14-dichloro-3,11-dimethyl-1,3,9,11-tetrahydro-5,13-dioxa-7,15-diazadiimidazo-[4,5-b:4′,5′-m]pentacene-2,10-dione), shows an X-ray powder diagram consisting of only ca 12 broad peaks. Indexing was not possible. The structure was solved by global lattice energy minimizations. The program CRYSCA [Schmidt & Kalkhof (1999), CRYSCA. Clariant GmbH, Pigments Research, Frankfurt am Main, Germany] was used to predict the possible crystal structures in different space groups. By comparing simulated and experimental powder diagrams, the correct structure was identified among the predicted structures. Owing to the low quality of the experimental powder diagram the Rietveld refinements gave no distinctive results and it was difficult to prove the correctness of the crystal structure. Finally, the structure was confirmed to be correct by refining the crystal structure of an isostructural mixed crystal having a better X-ray powder diagram. The compound crystallizes in P\bar 1, Z = 1. The crystal structure consists of a very dense packing of molecules, which are connected by hydrogen bridges of the type N—H...O=C. This packing explains the observed insolubility. The work shows that crystal structures of molecular compounds may be solved by lattice energy minimization from diffraction data of limited quality, even when indexing is not possible.

scholarly journals Crystal structure of mechanochemically synthesized Ag2CdSnS4

2020 ◽  
Vol 75 (4) ◽  
pp. 393-402 ◽  
Author(s):  
Eva M. Heppke ◽  
Stefan Berendts ◽  
Martin Lerch
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Powder Diffraction ◽  
Mechanochemical Synthesis ◽  
Type Structure ◽  
Structural Investigations ◽  
Space Group ◽  
X Ray ◽  
Structure Space ◽  
Acta Crystallogr

AbstractAg2CdSnS4 was synthesized by a two step mechanochemical synthesis route. From a detailed analysis of the observed reflections in the X-ray powder diffraction pattern, the crystal structure proposed in the literature (space group Cmc21 [E. Parthé, K. Yvon, R. H. Deitch, Acta Crystallogr.1969, B25, 1164–1174; O. V. Parasyuk, I. D. Olekseyuk, L. V. Piskach, S. V. Volkov, V. I. Pekhnyo, J. Alloys Compd.2005, 399, 173–177]) is questionable. Our structural investigations presented in this contribution point to the fact that Ag2CdSnS4 crystallizes in the monoclinic wurtzkesterite-type structure (space group Pn). At around T = 200°C, a phase transition to the orthorhombic wurtzstannite-type structure (space group Pmn21) is observed.

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