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Space group determination: Difference between revisions
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* To prevent XDS from trying to find a better space group than the one with the lowest R<sub>meas</sub> (often P1), you could just use MAX_FAC_Rmeas= 1.0 | * To prevent XDS from trying to find a better space group than the one with the lowest R<sub>meas</sub> (often P1), you could just use MAX_FAC_Rmeas= 1.0 | ||
* Space group determination is not a trivial task. There is a number of difficulties that arise - | * Space group determination is not a trivial task. There is a number of difficulties that arise - | ||
** ambiguity of hand of screw axis (e.g. 3<sub>1</sub> versus 3<sub>2</sub>, or 6<sub>2</sub> versus 6<sub>4</sub>) | ** ambiguity of hand of screw axis (e.g. 3<sub>1</sub> versus 3<sub>2</sub>, or 6<sub>2</sub> versus 6<sub>4</sub>) - see the table above! | ||
** twinning may make a low-symmetry space group look like a high-symmetry one | ** twinning may make a low-symmetry space group look like a high-symmetry one | ||
* only when the structure is satisfactorily refined can the chosen space group be considered established and correct. Until then, it is just a hypothesis and its alternatives (see the table) should be kept in mind. | |||