Solution

​Firstly, if a particular unit cell is entered for a unit cell search in either of ConQuest or WebCSD the search algorithms will not miss any matches which should be hit for that particular search. The ConQuest search, however, only uses the reduced unit cell lengths to find matches due to known mathematical instabilities associated with inclusion of the unit cell angles (Andrews, Bernstein & Pelletier, Acta Cryst, 1980, A36, 248-252).

The unit cell search implementation in WebCSD takes into account the reduced cell angles as well as the lengths by using a more advanced methodology involving nearly Buerger-reduced cells (Andrews & Bernstein, Acta Cryst, 1988, A44, 1009-1018). This approach avoids the problems with instabilities and means that the unit cell search in WebCSD gives fewer false positive hits.


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