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Difficult datasets: Difference between revisions
tell about SILICON for small-molecule work
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If you used larger OSCILLATION_RANGE than 1°, you should increase [http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xds_parameters.html#MAXIMUM_ERROR_OF_SPINDLE_POSITION= MAXIMUM_ERROR_OF_SPINDLE_POSITION=] (default is 2°) because you expect larger deviations of experimentally determined and calculated phi positions of reflections. Same might apply to MAXIMUM_ERROR_OF_SPOT_POSITION= ; the default is 3 pixels which may be too low to account for broad reflections. If you don't do this, many reflections that violate these limits will not be used for geometry refinement, which may turn out to be unstable. | If you used larger OSCILLATION_RANGE than 1°, you should increase [http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xds_parameters.html#MAXIMUM_ERROR_OF_SPINDLE_POSITION= MAXIMUM_ERROR_OF_SPINDLE_POSITION=] (default is 2°) because you expect larger deviations of experimentally determined and calculated phi positions of reflections. Same might apply to MAXIMUM_ERROR_OF_SPOT_POSITION= ; the default is 3 pixels which may be too low to account for broad reflections. If you don't do this, many reflections that violate these limits will not be used for geometry refinement, which may turn out to be unstable. | ||
If your crystal diffracts to high angles (e.g. small molecules) then the absorption in the detector surface affects both position and intensity of the recorded x-rays. XDS has two parameters, SENSOR_THICKNESS and [[SILICON]], to take care of that. If the data are measured with a Pilatus detector, the defaults are ok. If however a CCD is used then both SENSOR_THICKNESS and SILICON should be adjusted manually - see [[SILICON]]. | |||
== optimizing the parameters for CORRECT == | == optimizing the parameters for CORRECT == | ||