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.

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.

scholarly journals A citation analysis of the Cambridge Crystallographic Data Centre

2001 ◽  
Vol 34 (3) ◽  
pp. 375-380 ◽  
Author(s):  
Jane Redman ◽  
Peter Willett ◽  
Frank H. Allen ◽  
Robin Taylor
Keyword(s):  
Citation Analysis ◽  
Basic Research ◽  
Crystallographic Data ◽  
Cambridge Structural Database ◽  
Cambridge Crystallographic Data Centre ◽  
Research Papers ◽  
Highly Cited Papers ◽  
Data Centre ◽  
Structural Database ◽  
Highly Cited

Citation analysis has been widely used to quantify the influence of research articles on the development of science. This paper reports a citation analysis of ten highly cited papers associated with the Cambridge Crystallographic Data Centre (CCDC), covering the variation of citation with time, the journals in which citations occur, and the types of organization and the geographic regions that use the Cambridge Structural Database. The ten most highly cited papers, comprising four database descriptions (CSD), two geometrical tabulations (TAB) and four basic research papers (RES), received a total of 8494 citations over the period 1981–1998, with more than half of these citations occurring in the literature published from 1995 onwards. The high citation rates of the database descriptions (3573 of 8494) indicate the value of crystallographic data. However, the large number of citations of the geometrical tables (3172) and the research papers (1767) indicate that this value resides not just in the raw data held in the Cambridge Structural Database, but also in the structural knowledge that can be derived from it. In the most recent years covered by the analysis (1995–1998), these ten CCDC publications have received more than 1000 citations per annum (CSD 507, TAB 398 and RES 153 citations per annum) and the detailed analysis shows that these papers, and the data that they discuss, are used not only by crystallographers but also by researchers across the entire range of the chemical sciences.

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 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.

scholarly journals WebCSD: the online portal to the Cambridge Structural Database

2010 ◽  
Vol 43 (2) ◽  
pp. 362-366 ◽  
Author(s):  
Ian R. Thomas ◽  
Ian J. Bruno ◽  
Jason C. Cole ◽  
Clare F. Macrae ◽  
Elna Pidcock ◽  
...  
Keyword(s):  
Molecular Similarity ◽  
Structural Information ◽  
Three Dimensional ◽  
Cambridge Structural Database ◽  
Cambridge Crystallographic Data Centre ◽  
Web Based ◽  
Data Centre ◽  
Online Portal ◽  
Internet Browser ◽  
Structural Database

WebCSD, a new web-based application developed by the Cambridge Crystallographic Data Centre, offers fast searching of the Cambridge Structural Database using only a standard internet browser. Search facilities include two-dimensional substructure, molecular similarity, text/numeric and reduced cell searching. Text, chemical diagrams and three-dimensional structural information can all be studied in the results browser using the efficient entry summaries and embedded three-dimensional viewer.

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 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.

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