Data type: char
Must appear in a looped list containing '_atom_site_label'
A 'disordered methyl assembly with groups 1 and 2'
B 'disordered sites related by a mirror'
S 'disordered sites independent of symmetry'
A code which identifies a cluster of atoms that show long range positional disorder but are locally ordered. Within each such cluster of atoms, _atom_site_disorder_group is used to identify the sites that are simultaneously occupied. This field is only needed if there is more than one cluster of disordered atoms showing independent local order.