For this section, refer to the following part of the Crystals manual for more
complete options and explanations on using its DLS/restraint options:
and for modelling rigid bodies (\REGULARISE):
Modelling/Creating the Rigid Body
Even though not 100% appropriate on this structure, as an example, we with to make a regularised rigid body of this 5 membered with with equal bond length and angles.
Warning: more detailed and more powerful options are giving in the Crystals Manual
To Regularize the ring
Refining selected atoms as a rigid body
If you already have directives in the list12 (parameter definition list), you would have to edit the list12 via the Refinement, Edit Directives menu option.
Following is the simplified version using the GUI which will create a brand new List12: