MAGICSQUASH: more versatile non-crystallographic averaging with mulitple constraints.

The simultaneous application of multiple constraints such as non-crystallographic symmetry averaging, solvent levelling, histogram matching and Sayre's equation has proven to be very effective for phase refinement and extension. An existing program for this purpose, SQUASH, has been altered to increase the flexibility of its non-crystallographic symmetry averaging. The modified program, MAGICSQUASH, can handle multiple-domain averaging and multiple space group averaging and has aided in the solution of several structures. Examples are described which include the first simultaneous application of solvent levelling, histogram matching and Sayre's equation in two crystal forms while averaging between them.