Crystallographic data of double antisymmetry space groups

2014 ◽  
Vol 70 (4) ◽  
pp. 373-381 ◽  
Author(s):  
Mantao Huang ◽  
Brian K. VanLeeuwen ◽  
Daniel B. Litvin ◽  
Venkatraman Gopalan
Keyword(s):  
General Position ◽  
Crystallographic Data ◽  
Symmetry Element ◽  
Space Groups ◽  
Displacement Vectors

This paper presents crystallographic data of double antisymmetry space groups, including symmetry-element diagrams, general-position diagrams and positions, with multiplicities, site symmetries, coordinates, spin vectors, roto vectors and displacement vectors.

scholarly journals Arrays with Local Centers of Symmetry in Space Groups Pca21 and Pna21

1998 ◽  
Vol 54 (6) ◽  
pp. 921-924 ◽  
Author(s):  
R. E. Marsh ◽  
V. Schomaker ◽  
F. H. Herbstein
Keyword(s):  
Crystallographic Data ◽  
Cambridge Structural Database ◽  
Cambridge Crystallographic Data Centre ◽  
Asymmetric Unit ◽  
Space Groups ◽  
Data Centre ◽  
Structural Database

Of the several hundred structures in the Cambridge Structural Database [version 4.6 (1992), Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, England] having space groups Pca21 or Pna21 and more than one molecule in the asymmetric unit (Z > 4), approximately three-quarters contain local centers of symmetry. These local centers, which are not crystallographic centers, occur predominantly near x = 1\over8, y = 1\over4 in Pca21 or near x = 1\over8, y = 0 in Pna21; this also holds for the limited number of examples we have examined of pseudo-centrosymmetric molecules with Z = 4. Local centers at these points create unusual correlations between corresponding atoms in the two molecules.

Handling cell-parameter errors in crystallographic data

2009 ◽  
Vol 42 (5) ◽  
pp. 798-809 ◽  
Author(s):  
James Haestier
Keyword(s):  
Single Crystal ◽  
Cell Parameter ◽  
Covariance Matrices ◽  
Crystallographic Data ◽  
New Method ◽  
Single Crystal Diffraction ◽  
Space Groups ◽  
Cell Parameters ◽  
Anisotropic Displacement Parameters ◽  
Atomic Coordinates

A new method is presented for handling errors on crystallographic data. In single-crystal diffraction experiments, two variance–covariance matrices are present, one for the cell parameters and the second for the refined parameters (atomic coordinates and anisotropic displacement parameters). These two matrices can be combined so that errors on derived parameters, such as bond distances, bond angles and TLS tensors, may be calculated more simply. The new method works for all space groups but there are limitations on its application to triclinic space groups. The method allows errors to be transformed between space groups.

Synthesis and crystal structures of two structurally related kryptoracemates

2017 ◽  
Vol 73 (7) ◽  
pp. 575-581 ◽  
Author(s):  
Philipp Kramer ◽  
Michael Bolte
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Crystal Packing ◽  
Symmetry Element ◽  
Inversion Symmetry ◽  
Asymmetric Unit ◽  
Chiral Molecules ◽  
Space Groups ◽  
Independent Molecules

Kryptoracemates are racemic compounds (pairs of enantiomers) that crystallize in Sohnke space groups (space groups that contain neither inversion centres nor mirror or glide planes nor rotoinversion axes). Thus, the two symmetry-independent molecules cannot be transformed into one another by any symmetry element present in the crystal structure. Usually, the conformation of the two enantiomers is rather similar if not identical. Sometimes, the two enantiomers are related by a pseudosymmetry element, which is often a pseudocentre of inversion, because inversion symmetry is thought to be favourable for crystal packing. We obtained crystals of two kryptoracemates of two very similar compounds differing in just one residue, namely rac-N-[(1S,2R,3S)-2-methyl-3-(5-methylfuran-2-yl)-1-phenyl-3-(pivalamido)propyl]benzamide, C27H32N2O3, (I), and rac-N-[(1S,2S,3R)-2-methyl-3-(5-methylfuran-2-yl)-1-phenyl-3-(propionamido)propyl]benzamide dichloromethane hemisolvate, C25H28N2O3·0.5CH2Cl2, (II). The crystals of both compounds contain both enantiomers of these chiral molecules. However, since the space groups [P212121 for (I) and P1 for (II)] contain neither inversion centres nor mirror or glide planes nor rotoinversion axes, there are both enantiomers in the asymmetric unit, which is a rather uncommon phenomenon. In addition, it is remarkable that (II) contains two pairs of enantiomers in the asymmetric unit. In the crystal, molecules are connected by intermolecular N—H...O hydrogen bonds to form chains or layered structures.

scholarly journals VRML general position diagrams of non-cubic magnetic space groups

2005 ◽  
Vol 61 (a1) ◽  
pp. c473-c473
Author(s):  
D. B. Litvin ◽  
J. Burke ◽  
N. Cordisco
Keyword(s):  
General Position ◽  
Space Groups

3,4-Lutidinium salts with the diiodidoaurate(I) anion: structure of [(3,4-lut)2H]+·[AuI2]−and of two polymorphs of [(3,4-lut)2H+]2·[AuI2]−·I−

2018 ◽  
Vol 74 (3) ◽  
pp. 289-294
Author(s):  
Cindy Döring ◽  
Zhihong Sui ◽  
Peter G. Jones
Keyword(s):  
General Position ◽  
Space Groups ◽  
Layer Structures ◽  
Different Types ◽  
Stacking Patterns

Reactions between potassium tetraiodidoaurate(III) and pyridine (py, C5H5N) or 3,4-lutidine (3,4-dimethylpyridine, 3,4-lut, C7H9N) were tested as possible sources of azaaromatic complexes of gold(III) iodide, but all identifiable products contained gold(I). The previously known structure dipyridinegold(I) diiodidoaurate(I), [Au(py)2]+·[AuI2]−, (3) [Adamset al.(1982).Z. Anorg. Allg. Chem.485, 81–91], was redetermined at 100 K. The reactions with 3,4-lutidine gave three different types of crystal in small quantities. 3,4-Dimethylpyridine–3,4-dimethylpyridinium diiodidoaurate(I), [(3,4-lut)2H]+·[AuI2]−, (1), consists of an [AuI2]−anion on a general position and two [(3,4-lut)2H]+cations across twofold axes. Bis(3,4-dimethylpyridine–3,4-dimethylpyridinium) diiodidoaurate(I) iodide, [(3,4-lut)2H+]2·[AuI2]−·I−, (2), crystallizes as two polymorphs, each forming pseudosymmetric inversion twins, in the space groupsP21andPc(but resemblingP21/mandP2/c), respectively. These are essentially identical layer structures differing only in their stacking patterns and thus might be regarded as polytypes.

VRML general position diagrams of magnetic space groups

2006 ◽  
Vol 39 (4) ◽  
pp. 620-620
Author(s):  
J. S. Burke ◽  
N. R. Cordisco ◽  
D. B. Litvin
Keyword(s):  
General Position ◽  
Magnetic Moments ◽  
Three Dimensional ◽  
Space Groups

Three-dimensional general position diagrams of the superfamilies of all non-cubic magnetic space groups have been developed. The diagrams can be rotated and zoomed to aid in the visualization of the general position diagrams and include both the general positions of the atoms and the general orientations of the associated magnetic moments.

scholarly journals The space groups of point group C 3: some corrections, some comments

2002 ◽  
Vol 58 (5) ◽  
pp. 893-899 ◽  
Author(s):  
Richard E. Marsh
Keyword(s):  
Point Group ◽  
Crystallographic Data ◽  
Cambridge Structural Database ◽  
Cambridge Crystallographic Data Centre ◽  
Space Group ◽  
Space Groups ◽  
Data Centre ◽  
Group Assignment ◽  
Structural Database

A survey of the October 2001 release of the Cambridge Structural Database [Cambridge Structural Database (1992). Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, England] has uncovered approximately 675 separate apparently reliable entries under space groups P3, P3_1, P3_2 and R3; in approximately 100 of these entries, the space-group assignment appears to be incorrect. Other features of these space groups are also discussed.

Basic crystallographic data of anhydrous hexaamidocyclotriphosphazene and its monohydrate

1981 ◽  
Vol 46 (7) ◽  
pp. 1625-1628
Author(s):  
Milan Kouřil ◽  
Zdirad Žák
Keyword(s):  
Single Crystal ◽  
Least Squares ◽  
Least Squares Method ◽  
Lattice Parameters ◽  
Crystallographic Data ◽  
Crystal Data ◽  
Space Groups

Powder photographs of (PN(NH2)2)3 and (PN(NH2)2)3.H2O were indexed based on the lattice parameters obtained from the single crystal data, and the parameters were refined by using the least-squares method. The space groups belonging to the two crystalline substances are Pcba (Z = 8) and P1 (P1) (Z = 2), respectively.

Microstructure and crystal symmetry of Pb2Sr2(Y/Ca)Cu3O9−δ

1990 ◽  
Vol 48 (4) ◽  
pp. 64-65
Author(s):  
Y. P. Lin ◽  
J. S. Xue ◽  
J. E. Greedan
Keyword(s):  
Electron Diffraction ◽  
High Temperature Superconductors ◽  
Carbon Film ◽  
Basic Structure ◽  
Crystal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
New Family ◽  
Convergent Beam

A new family of high temperature superconductors based on Pb2Sr2YCu3O9−δ has recently been reported. One method of improving Tc has been to replace Y partially with Ca. Although the basic structure of this type of superconductors is known, the detailed structure is still unclear, and various space groups has been proposed. In our work, crystals of Pb2Sr2YCu3O9−δ with dimensions up to 1 × 1 × 0.25.mm and with Tc of 84 K have been grown and their superconducting properties described. The defects and crystal symmetry have been investigated using electron microscopy performed on crushed crystals supported on a holey carbon film.Electron diffraction confirmed x-ray diffraction results which showed that the crystals are primitive orthorhombic with a=0.5383, b=0.5423 and c=1.5765 nm. Convergent Beam Electron Diffraction (CBED) patterns for the and axes are shown in Figs. 1 and 2 respectively.

Symmetry breaking in convergent-beam diffraction

1989 ◽  
Vol 47 ◽  
pp. 480-481
Author(s):  
D.J. Eaglesham
Keyword(s):  
Symmetry Breaking ◽  
Point Group ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Space Groups ◽  
Atomic Displacements ◽  
Small Probe ◽  
Phase Sensitive ◽  
Convergent Beam

Convergent Beam Electron Diffraction is now almost routinely used in the determination of the point- and space-groups of crystalline samples. In addition to its small-probe capability, CBED is also postulated to be more sensitive than X-ray diffraction in determining crystal symmetries. Multiple diffraction is phase-sensitive, so that the distinction between centro- and non-centro-symmetric space groups should be trivial in CBED: in addition, the stronger scattering of electrons may give a general increase in sensitivity to small atomic displacements. However, the sensitivity of CBED symmetry to the crystal point group has rarely been quantified, and CBED is also subject to symmetry-breaking due to local strains and inhomogeneities. The purpose of this paper is to classify the various types of symmetry-breaking, present calculations of the sensitivity, and illustrate symmetry-breaking by surface strains.CBED symmetry determinations usually proceed by determining the diffraction group along various zone axes, and hence finding the point group. The diffraction group can be found using either the intensity distribution in the discs

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