International
Tables for
Crystallography
Volume G
Definition and exchange of crystallographic data
Edited by J. R. Hester and B. McMahon

International Tables for Crystallography (2026). Vol. G. Early view chapter
https://doi.org/10.1107/97809553602060001011

Chapter 4.2 Core dictionary (coreCIF)


Index

Core dictionary version 3.3.0

_geom_hbond.site_symmetry_A

Name:
_geom_hbond.site_symmetry_A

Alias:
_geom_hbond_site_symmetry_A

Definition:

   
     Data item specifying the symmetry operation codes applied to the atom
     sites involved in a specific geometric configuration or other correlated
     behaviour.

     The symmetry code of each atom site as the symmetry-equivalent position
     number 'n' and the cell translation number 'pqr'. These numbers are
     combined to form the code 'n pqr' or n_pqr.

     The character string n_pqr is composed as follows:

     n refers to the symmetry operation that is applied to the
     coordinates stored in _atom_site.fract_xyz. It must match
     a number given in _space_group_symop.id (or one of its
     aliases, such as _symmetry_equiv_pos_site_id).

     p, q and r refer to the translations that are subsequently
     applied to the symmetry transformed coordinates to generate
     the related atom position. These translations (x,y,z) are related
     to (p,q,r) by the relations
          p = 5 + x
          q = 5 + y
          r = 5 + z

Examples:

4 4th symmetry operation applied.
7_645 7th symm. posn.; +a on x; -b on y.
. No symmetry or translation to site.

Type: Symop


Enumeration default: 1_555

Category:
geom_hbond








































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