International
Tables for
Crystallography
Volume A
Space-group symmetry
Edited by Th. Hahn

International Tables for Crystallography (2006). Vol. A, ch. 2.2, pp. 17-18

Section 2.2.3. Headline

Th. Hahna* and A. Looijenga-Vosb

aInstitut für Kristallographie, Rheinisch-Westfälische Technische Hochschule, Aachen, Germany, and bLaboratorium voor Chemische Fysica, Rijksuniversiteit Groningen, The Netherlands
Correspondence e-mail:  hahn@xtl.rwth-aachen.de

2.2.3. Headline

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The description of each plane group or space group starts with a headline on a left-hand page, consisting of two (sometimes three) lines which contain the following information, when read from left to right.

First line

  • (1) The short international (Hermann–Mauguin) symbol for the plane or space group. These symbols will be further referred to as Hermann–Mauguin symbols. A detailed discussion of space-group symbols is given in Chapter 12.2[link] , a brief summary in Section 2.2.4[link].

    Note on standard monoclinic space-group symbols: In order to facilitate recognition of a monoclinic space-group type, the familiar short symbol for the b-axis setting (e.g. [P2_{1}/c] for No. 14 or [C2/c] for No. 15) has been adopted as the standard symbol for a space-group type. It appears in the headline of every description of this space group and thus does not carry any information about the setting or the cell choice of this particular description. No other short symbols for monoclinic space groups are used in this volume (cf. Section 2.2.16[link]).

  • (2) The Schoenflies symbol for the space group.

    Note: No Schoenflies symbols exist for the plane groups.

  • (3) The short international (Hermann–Mauguin) symbol for the point group to which the plane or space group belongs (cf. Chapter 12.1[link] ).

  • (4) The name of the crystal system (cf. Table 2.1.2.1[link] ).

Second line

  • (5) The sequential number of the plane or space group, as introduced in IT (1952)[link].

  • (6) The full international (Hermann–Mauguin) symbol for the plane or space group.

    For monoclinic space groups, the headline of every description contains the full symbol appropriate to that description.

  • (7) The Patterson symmetry (see Section 2.2.5[link]).

Third line

This line is used, where appropriate, to indicate origin choices, settings, cell choices and coordinate axes (see Section 2.2.2[link]). For five orthorhombic space groups, an entry `Former space-group symbol' is given; cf. Chapter 1.3[link] , Note (x)[link] .

References

International Tables for X-ray Crystallography (1952). Vol. I, edited by N. F. M. Henry & K. Lonsdale. Birmingham: Kynoch Press. [Revised editions: 1965, 1969 and 1977. Abbreviated as IT (1952).]








































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