Crystallographic Information Framework

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Core dictionary (coreCIF) version 2.4.5


'_geom_torsion_atom_site_label_1' '_geom_torsion_atom_site_label_2' '_geom_torsion_atom_site_label_3' '_geom_torsion_atom_site_label_4'


   The labels of the four atom sites which define the torsion angle
   specified by _geom_torsion. These must match codes specified as
   _atom_site_label in the atom list. The torsion-angle definition
   should be that of Klyne and Prelog. The vector direction
   *_label_2 to *_label_3 is the viewing direction, and the torsion
   angle is the angle of twist required to superimpose the
   projection of the vector between site 2 and site 1 onto the
   projection of the vector between site 3 and site 4. Clockwise
   torsions are positive, anticlockwise torsions are negative.

   Ref: Klyne, W. & Prelog, V. (1960). Experientia, 16, 521-523.

Appears in list as essential element of loop structure

Must match data name_atom_site_label

Type: char

Category: geom_torsion