Application and comparison of different tests on twinning by merohedry

1999 ◽  
Vol 55 (5) ◽  
pp. 745-751 ◽  
Author(s):  
V. Kahlenberg
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Structure Determination ◽  
Data Sets ◽  
Crystal Data ◽  
Test Procedures ◽  
Preliminary Stage ◽  
Volume Fractions ◽  
Inorganic Crystal

Three different tests on twinning by merohedry from the literature have been applied to single-crystal data sets of five different inorganic crystal structures. Although the three test procedures differ significantly with regard to their efficiency, in both detecting the existence of twinning and estimating the volume fractions of the twin individuals, they represent useful tools in the early stages of a structure analysis and should be applied routinely in the preliminary stage of a structure determination whenever a twinning by merohedry is possible.

Zur Struktur und Dotierung von Selenosilikaten: die Kristallstruktur von Er2SeSiO4 und Er3,75Ca0,25Se2,75Cl0,25Si2O7 Structure and Doping of Seleno Silicates: the Crystal Structures of Er2SeSiO4 and Er3,75Ca0,25Se2,75Cl0,25Si2O7

1994 ◽  
Vol 49 (6) ◽  
pp. 733-740 ◽  
Author(s):  
Klaus Stöwe
Keyword(s):  
Crystal Structures ◽  
Structure Analysis ◽  
Rare Earths ◽  
Structure Determination ◽  
Lattice Parameters ◽  
Energy Dispersive ◽  
Space Group ◽  
X Ray ◽  
By Products

Well-shaped brown and pink isometric crystals were obtained as by-products of the synthesis of erbium selenides from the elements in evacuated and sealed silica ampoules with graphite inlets. They could be identified as erbium seleno mono- and disilicates by energy dispersive X-ray fluorescence and X-ray structure determination. The monosilicate Er2SeSiO4 crystallizes isotypically to Nd2SeSiO4 in the space group Pbcm with the lattice parameters a = 600.2(2), b = 688.0(2), c = 1075.2(2) pm and represents the second known seleno inosilicate of the rare earths. From X-ray structure analysis an isotypic relation between the disilicate Er3,75Ca0,25Se2,75Cl0,25Si2O7 and the compound Sm4S3Si2O7 was found, the former crystallizing in the space group I41/amd with the lattice parameters a - 1177.7(2) and c = 1376.5(2) pm. The doping o f the sorosilicate with the elements Ca and Cl originated from contam inations in the graphit inlets used in the procedure

Lewis-Base Adducts of Group 1B Metal(I) Compounds. XXI The Crystal and Molecular Structures of the Unsolvated Forms of Dibromotris(triphenylphosphine)dicopper(I) and 'step' Tetrabromotetrakis(triphenyl-phosphine)tetracopper(I)

1985 ◽  
Vol 38 (8) ◽  
pp. 1243 ◽  
Author(s):  
JC Dyason ◽  
LM Engelhardt ◽  
C Pakawatchai ◽  
PC Healy ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Molecular Structures ◽  
Lewis Base ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Triphenyl Phosphine ◽  
X Ray ◽  
Crystal And Molecular Structures

The crystal structures of the title compounds have been determined by single-crystal X-ray diffraction methods at 295 K. Crystal data for (PPh3)2CuBr2Cu(PPh3) (1) show that the crystals are iso-morphous with the previously studied chloro analogue, being monoclinic, P21/c, a 19.390(8), b 9.912(5), c 26.979(9) Ǻ, β 112,33(3)°; R 0.043 for No 3444. Cu( trigonal )- P;Br respectively are 2.191(3); 2.409(2), 2.364(2) Ǻ. Cu(tetrahedral)- P;Br respectively are 2.241(3), 2.249(3); 2.550(2), 2.571(2) Ǻ. Crystals of 'step' [PPh3CuBr]4 (2) are isomorphous with the solvated bromo and unsolvated iodo analogues, being monoclinic, C2/c, a 25.687(10), b 16.084(7), c 17.815(9) Ǻ, β 110.92(3)°; R 0.072 for No 3055. Cu( trigonal )- P;Br respectively are 2.206(5); 2.371(3), 2.427(2) Ǻ. Cu(tetrahedral)- P;Br are 2.207(4); 2.446(2), 2.676(3), 2.515(3) Ǻ.

Kristallzucht und Strukturaufklärung von K2[Pt(CN)4Cl2], K2[Pt(CN)4Br2], K2[Pt(CN)4I2] und K2[Pt(CN)4Cl2] · 2H2O/ Crystal Growth and Crystal Structure Determination of K2[Pt(CN)4Cl2], K2[Pt(CN)4Br2], K2[Pt(CN)4I2] and K2[Pt(CN)4]Cl2] · 2H2O

2004 ◽  
Vol 59 (5) ◽  
pp. 567-572 ◽  
Author(s):  
Claus Mühle ◽  
Andrey Karpov ◽  
Jürgen Nuss ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Infrared Spectroscopy ◽  
Crystal Growth ◽  
Single Crystal ◽  
Structure Determination ◽  
Spectroscopy Data ◽  
Crystal Data ◽  
X Ray ◽  
Raman And Infrared Spectroscopy

Abstract Crystals of K2Pt(CN)4Br2, K2Pt(CN)4I2 and K2Pt(CN)4Cl2 ·2H2O were grown, and their crystal structures have been determined from single crystal data. The structure of K2Pt(CN)4Cl2 has been determined and refined from X-ray powder data. All compounds crystallize monoclinicly (P21/c; Z = 2), and K2Pt(CN)4X2 with X = Cl, Br, I are isostructural. K2Pt(CN)4Cl2: a = 708.48(2); b = 903.28(3); c = 853.13(3) pm; β = 106.370(2)°; Rp = 0.064 (N(hkl) = 423). K2Pt(CN)4Br2: a = 716.0(1); b = 899.1(1); c = 867.9(1) pm; β = 106.85(1)°; R(F)N′ = 0.026 (N’(hkl) = 3757). K2Pt(CN)4I2: a = 724.8(1); b = 914.5(1); c = 892.1(1) pm; β = 107.56(1)°; R(F)N′ = 0.025 (N’(hkl) = 2197). K2Pt(CN)4Cl2 ·2H2O: a = 763.76(4); b = 1143.05(6); c = 789.06(4) pm; β = 105.18(1)°; R(F)N′ = 0.021 (N’(hkl) = 2281). Raman and infrared spectroscopy data are reported.

Hydrothermal Crystal Growth and Crystal Structures of the Mercury(II) Chromates(VI) α-HgCrO4, β-HgCrO4, and HgCrO4·H2O

2006 ◽  
Vol 61 (6) ◽  
pp. 708-714 ◽  
Author(s):  
Berthold Stöger ◽  
Matthias Weil
Keyword(s):  
Crystal Growth ◽  
Single Crystal ◽  
Single Crystals ◽  
Crystal Structures ◽  
Chromic Acid ◽  
Structure Type ◽  
Data Sets ◽  
Hydrothermal Conditions ◽  
Hydrothermal Crystal Growth ◽  
Structure Factors

Single crystals of α-HgCrO4, β -HgCrO4 and HgCrO4 ・ H2O were obtained by reacting yellow HgO in chromic acid of various concentrations under hydrothermal conditions at 200 °C (4 d). All crystal structures were solved and refined from single crystal diffractometer data sets [α-HgCrO4: P21/n, Z = 4, a = 5.5079(8), b = 8.5266(12), c = 7.3503(10) Å , β = 94.022(3)°, 955 structure factors, R[F2 > 2σ (F2)] = 0.0296; β -HgCrO4: Cmcm, Z = 4, a = 5.7187(9), b = 9.0169(14), c = 7.0114(11) Å, 361 structure factors, R[F2 > 2σ (F2)] = 0.0275; HgCrO4 ・ H2O: P1̅, Z = 2, a=5.6157(15), b =6.1115(16), c= 7.590(2) Å , α =108.850(5), β =91.666(5), γ =116.569(5)°, 1235 structure factors, R[F2 > 2σ (F2)] = 0.0316]. The previously reported structure of α-HgCrO4 has been re-determined. It contains distorted [HgO7] pentagonal bipyramids in which the short bonds are directed towards the apices. The new polymorph β -HgCrO4 adopts the CrVO4 (β -CrPO4) structure type and is composed of slightly distorted [HgO6] octahedra. The previously unknown monohydrate HgCrO4 ・ H2O crystallizes in an unique structure and is composed of one nearly regular [HgO4(H2O)2] octahedron and one considerably distorted [HgO6] octahedron. All three structures contain tetrahedral chromate anions CrO42− as the second building units with average Cr-O distances of ca. 1.65 Å

Structure of caesium disulfate at 120 and 273 K

2009 ◽  
Vol 65 (5) ◽  
pp. 551-557 ◽  
Author(s):  
Kenny Ståhl ◽  
Rolf W. Berg ◽  
K. Michael Eriksen ◽  
Rasmus Fehrmann
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Metal Structure ◽  
Structure Type ◽  
The Other ◽  
Crystal Data ◽  
Remarkable Similarity ◽  
Disorder Transition ◽  
X Ray

The crystal structures of Cs2S2O7 at 120 and 273 K have been determined from X-ray single-crystal data. Caesium disulfate represents a new structure type with a uniquely high number of independent formula units at 120 K: In one part caesium ions form a tube surrounding the disulfate ions, [Cs8(S2O7)6+] n ; in the other part a disulfate double-sheet sandwiches a zigzagging caesium ion chain, [Cs2(S2O7)6−] n . Caesium disulfate shows an isostructural order–disorder transition between 230 and 250 K, where two disulfate groups become partially disordered above 250 K. The Cs+-ion arrangement shows a remarkable similarity to the high-pressure RbIV metal structure.

The Anion [Co(C8H12)2]–. A Comparative Study of the Crystal Structures of [{K(18-crown-6)}2(C5H5)][Co(C8H12)2] and Co(C8H12)(C8H13)

2009 ◽  
Vol 64 (8) ◽  
pp. 985-988 ◽  
Author(s):  
Jian-Qiang Wang ◽  
Thomas F. Fässler
Keyword(s):  
Crystal Structure ◽  
Crown Ether ◽  
Comparative Study ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Determination ◽  
Cobalt Complex ◽  
Crystal Structure Determination ◽  
X Ray ◽  
Cyclopentadienyl Anion

The cobalt complex [{K(18-crown-6)}2(C5H5)]- [Co(C8H12)2]・(THF)2 (3) has been synthesized and characterized by X-ray single-crystal structure determination. The crystal structure of Co(C8H12)(C8H13) (2) has been reinvestigated and compared with the structure of 3. The 1,5-cyclooctadiene (C8H12) and C8H13 ligands are coordinated in an η4 and η3 fashion, respectively. The cyclopentadienyl anion in [{K(18-crown-6)}2(C5H5)]+ in 3 is η5-coordinated to the two crown ether-encapsulated potassium cations

The use of Mo Kα radiation in the assignment of the absolute configuration of light-atom molecules; the importance of high-resolution data

2014 ◽  
Vol 70 (4) ◽  
pp. 660-668 ◽  
Author(s):  
Eduardo C. Escudero-Adán ◽  
Jordi Benet-Buchholz ◽  
Pablo Ballester
Keyword(s):  
High Resolution ◽  
Crystal Structures ◽  
Structure Determination ◽  
Great Majority ◽  
Data Sets ◽  
Light Atom ◽  
High Resolution Data ◽  
The Absolute ◽  
Absolute Structure

Recent studies have confirmed the usefulness of the Hooft and Parsons methodologies for determination of the absolute crystal structures of enantiopure light-atom compounds using CuKα radiation. While many single-crystal diffractometers used for small-molecule structure determination are equipped with molybdenum anodes, use of data from such instruments for the absolute structure determination of light-atom crystal structures is rarely documented and has often been found to be unsuccessful. The Hooft and Parsons methodologies have been applied to 44 data sets obtained from single crystals containing light-atom molecules of known chirality using Mo Kαradiation. Several factors influencing the calculation of accurate and precise values for the Hooft and Parsons parameters obtained from these data sets have been identified, the inclusion of high-resolution diffraction data being particularly important. The correct absolute structure was obtained in all cases, with the standard uncertainties of the final absolute structure parameters below 0.1 for the great majority.

scholarly journals Structure determination from X-ray powder diffraction data at low resolution

2014 ◽  
Vol 70 (a1) ◽  
pp. C143-C143
Author(s):  
Hongliang Xu
Keyword(s):  
Single Crystal ◽  
Diffraction Pattern ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Direct Methods ◽  
Atomic Resolution ◽  
Powder Diffraction Data ◽  
Low Resolution

Knowledge of the structural arrangement of atoms in solids is necessary to facilitate the study of their properties. The best and most detailed structural information is obtained when the diffraction pattern of a single crystal a few tenths of a millimeter in each dimension is analyzed, but growing high-quality crystals of this size is often difficult, sometimes impossible. However, many crystallization experiments that do not yield single crystals do yield showers of randomly oriented micro-crystals that can be exposed to X-rays simultaneously to produce a powder diffraction pattern. Direct Methods routinely solve crystal structures when single-crystal diffraction data are available at atomic resolution (1.0-1.2Å), but fail to determine micro-crystal structures due to reflections overlapping and low-resolution powder diffraction data. By artificially and intelligently extending the measured data to atomic resolution, we have successfully solved structures having low-resolution diffraction data that were hard to solve by other direct-method based computation procedures. The newly developed method, Powder Shake-and-Bake, is implemented in a computer program PowSnB. PowSnB can be incorporated into the state-of-the-art software package EXPO that includes powder data reduction, structure determination and structure refinement. The new combination could have potential to solve structures that have never been solved before by direct-methods approach.

Strukturbestimmung von Ga[GaCl4] und α-Ga[GaBr4] nach Kristallisation aus Halogenbenzolen / Structure Determination of Ga[GaCl4] and α-Ga[GaBr4] Crystallized from Halobenzene Solvents

1987 ◽  
Vol 42 (5) ◽  
pp. 553-556 ◽  
Author(s):  
H. Schmidbaur ◽  
R. Nowak ◽  
W. Bublak ◽  
P. Burkert ◽  
B. Huber ◽  
...  
Keyword(s):  
Single Crystals ◽  
Crystal Structures ◽  
Structure Determination ◽  
Nmr Spectra ◽  
Approximate Calculation ◽  
Crystal Data ◽  
Crystalline Powder ◽  
Powder Samples ◽  
Asymmetry Parameters

Single crystals of Ga[GaCl4] and α-Ga[GaBr4] have been obtained by crystallization from chlorobenzene and bromobenzene, respectively. The crystal structures of the two compounds, determined previously only on the basis of photographic data, were refined to a more satisfactory level of accuracy. The results confirm the presence of tetrahedral GaX4- anions as thecounterions to dodecahedrally coordinated Ga+ cations. The gallium-halogen distances in these dodecahedral arrays fall into four classes, thus resulting in a significant asymmetry of the Ga(I) center. This deviation from ideal S4 symmetry is also apparent in the 69Ga NMR spectra of the crystalline powder samples. Approximate calculation of the data leads to asymmetry parameters (η) of 0.44 and 0.27 for the chloride and bromide, respectively. Crystal data Ga[GaCl4]: Pnna (#52), a = 7.200(1), b = 9.625(1), c = 9.498(1) Å; Z = 4. For α-Ga[GaBr4]: Pnna, a = 7.528(1), b = 9.972(1), c = 10.010(1) Å, Z = 4.

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