A note on practical aspects of the application of DIRDIF, a procedure for structure elucidation when a part of the structure is known

The DIRDIF procedure (direct methods applied to difference structures) has been tested on a variety of structures. It is shown that errors in the atomic positions of approximately 0.3 Å are acceptable, that the minimum size of the known molecular fragment is about 10% of the total scattering power, and that lack of knowledge about the unit-cell contents is not deleterious