Section 13.1.2.3. Exploitation of noncrystallographic symmetry

In order to draw structural information from noncrystallographic symmetry, the different classes of subunit must provide different information. Cases of pseudo-crystallographic symmetry, where subunits are almost in an arrangement of higher crystallographic symmetry, are difficult to exploit by the techniques discussed in this chapter. Typically only weak reflections (those which would be forbidden by the higher symmetry if it were exact) provide extra information. This situation often arises in case (6), Table 13.1.2.1. Similarly in cases (7) and (8), comparison of crystals whose cell dimensions or contents are only slightly altered gives little new information.