Based on the provided search results, the video file "dv5020sup5.mp4" (associated with H21(1) in the context of symmetry) is a visual aid illustrating how a "giant asymmetric unit" behaves under symmetry operations in crystallography.
Zn ions, for example, are located directly on the rotation axis. H21(1).mp4
The minimum structural unit (the dimer) that, when acted upon by space group symmetry operations, generates the full crystal structure. Based on the provided search results, the video