If strict
non-crystallographic symmetry is imposed, the crystal symmetry interactions
cannot be computed because of nonequivalent environments (see
Chapter 16). Instead, only the
interaction between non-crystallographically related molecules is
computed using the 
and 
functional forms, i.e.,
The atom/group search and the update of the interaction list are carried out analogously to the intramolecular case. (Refer to Chapter 16 for the definition of non-crystallographic symmetry operators.)