International
Tables for Crystallography Volume B Reciprocal space Edited by U. Shmueli © International Union of Crystallography 2006 
International Tables for Crystallography (2006). Vol. B, ch. 2.2, pp. 228230
Section 2.2.8. Other multisolution methods applied to small molecules ^{a}Dipartimento Geomineralogico, Campus Universitario, I70125 Bari, Italy 
In very complex structures a large initial set of known phases seems to be a basic requirement for a structure to be determined. This aim can be achieved, for example, by introducing a large number of permutable phases into the initial set. However, the introduction of every new symbol implies a fourfold increase in computing time, which, even in fast computers, quickly leads to computingtime limitations. On the other hand, a relatively large starting set is not in itself enough to ensure a successful structure determination. This is the case, for example, when the triplet invariants used in the initial steps differ significantly from zero. New strategies have therefore been devised to solve more complex structures.

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