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