scholarly journals Use of software to search for higher symmetry: space group C2

2001 ◽  
Vol 57 (6) ◽  
pp. 800-805 ◽  
Author(s):  
Richard E. Marsh ◽  
Anthony L. Spek
Keyword(s):  
Cambridge Structural Database ◽  
Higher Symmetry ◽  
Space Group ◽  
Space Groups ◽  
Bond Lengths ◽  
Structural Database ◽  
Symmetry Space ◽  
Coordinate Data ◽  
Symmetry Space Group

From a search of the October 2000 release of the Cambridge Structural Database we find coordinate data for approximately 1500 entries under space group No. 5: C2 or, occasionally, A2, I2 or B112. Software designed to detect cases of missed higher symmetry identified 144 entries for detailed inspection. Of these, 50 should, we believe, be revised to space groups of higher symmetry. The most common revision is to space group C2/m, which entails adding a center of inversion and usually results in important changes in bond lengths and angles.

Space groups of the diamond polytypes

1993 ◽  
Vol 8 (11) ◽  
pp. 2835-2839 ◽  
Author(s):  
A.W. Phelps ◽  
W. Howard ◽  
D.K. Smith
Keyword(s):  
Systematic Method ◽  
Space Group ◽  
Space Groups ◽  
Symmetry Space ◽  
Atomic Coordinates ◽  
Symmetry Space Group

Space groups and atomic coordinates for the 4H, 6H, 8H, 10H, 15R, and 21R polytypes of diamond are presented. The systematic method used to determine the highest symmetry space group for diamond polytypes is described.

Non-centrosymmetric racemates: space-group frequencies and conformational similarities between crystallographically independent molecules

2000 ◽  
Vol 56 (4) ◽  
pp. 715-719 ◽  
Author(s):  
Bjørn Dalhus ◽  
Carl Henrik Görbitz
Keyword(s):  
Cambridge Structural Database ◽  
Asymmetric Unit ◽  
Space Group ◽  
Space Groups ◽  
Common Space ◽  
Molecular Superposition ◽  
Structural Database ◽  
The Common ◽  
The Mean ◽  
Independent Molecules

DL-Allylglycine (DL-2-amino-4-pentenoic acid, C5H9NO2) yields crystals with Pca21 symmetry and two crystallographically independent yet pseudo-inversion-related enantiomers. The distribution among the common space groups of other crystalline racemates with more than one molecule in the asymmetric unit has been established. The conformational similarities between crystallographically independent enantiomers in 114 non-centrosymmetric racemates were quantified using the r.m.s. deviation for a molecular superposition. The analysis shows that in the majority of crystals the conformations of the crystallographically independent molecules are very similar with mean r.m.s. deviation = 0.190 Å. In almost 80% of the structures the mean r.m.s. deviations is in the interval 0–0.2 Å. It is estimated that racemates constitute 23% of the centrosymmetric organic structures in the Cambridge Structural Database.

scholarly journals N′-[(E)-4-Bromobenzylidene]-2-(4-isobutylphenyl)propanohydrazide

2009 ◽  
Vol 65 (6) ◽  
pp. o1184-o1185 ◽  
Author(s):  
Hoong-Kun Fun ◽  
Ching Kheng Quah ◽  
K. V. Sujith ◽  
B. Kalluraya
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Asymmetric Unit ◽  
Higher Symmetry ◽  
Space Group ◽  
Compound C ◽  
Benzene Rings ◽  
Independent Molecules ◽  
Symmetry Space ◽  
Symmetry Space Group

The asymmetric unit of the title compound, C20H23BrN2O, contains two independent molecules (AandB), in which the orientations of the 4-isobutylphenyl units are different. The dihedral angle between the two benzene rings is 88.45 (8)° in moleculeAand 89.87 (8)° in moleculeB. MoleculesAandBare linked by a C—H...N hydrogen bond. In the crystal, molecules are linked into chains running along theaaxis by intermolcular N—H...O and C—H...O hydrogen bonds. The crystal structure is further stabilized by C—H...π interactions. The presence of pseudosymmetry in the structure suggests the higher symmetry space groupPbca. However, attempts to refine the structure in this space group resulted in a disorder model with highR(0.097) andwR(0.257) values. The crystal studied was an inversion twin with a 0.595 (4):0.405 (4) domain ratio.

Pseudosymmetry in ammonium [(carboxymethyl)sulfanyl]acetate

2003 ◽  
Vol 59 (11) ◽  
pp. o656-o658 ◽  
Author(s):  
Jan K. Maurin ◽  
Michał Pawłowski ◽  
Zbigniew Czarnocki
Keyword(s):  
Acetic Acid ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Three Dimensional ◽  
Carboxylate Anion ◽  
Dimensional Structure ◽  
Higher Symmetry ◽  
Space Group ◽  
Symmetry Space ◽  
Symmetry Space Group

The structure of the title compound, NH4 +·C4H5O4S−, is composed of monocarboxylate anions of [(carboxymethyl)sulfanyl]acetic acid linked into infinite chains via strong O—H...O− hydrogen bonds. The three-dimensional structure is completed by the ammonium cations, which interlink neighbouring chains via N—H...O hydrogen bonds. Solution and refinement in the true space group Pn led to an unambiguous position for the single carboxyl H atom. In the higher symmetry space group P2/n, the carboxylate anion would be located on a twofold axis.

scholarly journals Some more space-group corrections

2014 ◽  
Vol 70 (9) ◽  
pp. 834-836 ◽  
Author(s):  
Lawrence M. Henling ◽  
Richard E. Marsh
Keyword(s):  
Crystal Structures ◽  
Cambridge Structural Database ◽  
Space Group ◽  
Space Groups ◽  
Structural Database

A survey of approximately 100 000 entries in recent releases of the Cambridge Structural Database (CSD) has uncovered 156 crystal structures that were apparently described in inappropriate space groups. We have revised these space groups and prepared CIFs containing the new coordinates and brief comments describing the revisions.

Imidazolidin-2-one: pseudosymmetry and twinning

2013 ◽  
Vol 69 (12) ◽  
pp. 1534-1536 ◽  
Author(s):  
Christina Taouss ◽  
Peter G. Jones ◽  
Daniel J. Tindall
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Chair Conformation ◽  
Membered Ring ◽  
Higher Symmetry ◽  
Space Group ◽  
Compound C ◽  
Symmetry Space ◽  
Symmetry Space Group

The title compound, C3H6N2O, crystallizes with imposed twofold symmetry in the space groupI41/a. The five-membered ring displays a half-chair conformation. N—H...O hydrogen bonds connect the molecules to formR22(8) rings and thence ribbons parallel to theaandbaxes. These intersectviaO2H2rings involving longer H...O contacts. The crystal was merohedrally twinned. Preliminary indications of the higher symmetry space groupI41/amd, which would require the ring to be planar, proved to be incorrect. A previous brief report of the structure inFdd2 is also probably incorrect.

scholarly journals Space groups P1 and Cc: how are they doing?

2009 ◽  
Vol 65 (6) ◽  
pp. 782-783 ◽  
Author(s):  
Richard E. Marsh
Keyword(s):  
Cambridge Structural Database ◽  
Space Group ◽  
Space Groups ◽  
Structural Database ◽  
Low Symmetry

A survey of recent entries in the Cambridge Structural Database suggests that the percentage of structures described in space groups of inappropriately low symmetry has decreased from about 10% in the early 2000s to less than 5% today for space group Cc, but that for space group P1 it remains close to 8%.

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.

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