Section 25.2.1.10.2.2. Complex rotational and/or translational symmetry

For `improper' NC symmetry, where there are translational components and/or arbitrary rotation angles involved, separate envelope masks must be assigned to each molecule in the aggregate for both NC symmetry operator refinement and averaging. Initial operator refinement can proceed with spherical masks of an appropriate radius centred on the centre of mass of each molecule in the aggregate. As in the `proper' NC symmetry case, one can also use masks created by hand or generated from atomic coordinates for operator refinement, but hand-traced masks will be desired for the actual averaging. The NC symmetry operator refinement is carried out within the program LSQROTGEN (batch).