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Optimisation: Difference between revisions
paragraph about beam divergence and mosaicity
(→Re-INTEGRATEing with the correct spacegroup and refined geometry: fine-slicing of profiles) |
(paragraph about beam divergence and mosaicity) |
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xds_par | xds_par | ||
and thereby re-run the INTEGRATE and CORRECT steps. This has the advantage that the refined geometry parameters (from CORRECT) are recycled into INTEGRATE, which sometimes leads to better R-factors. It also results in the spacegroup's restraints on the unit cell parameters being used for the prediction of spot positions; these are therefore slightly more accurate. Fine-slicing of profiles has been found to be advantageous at least for Pilatus detectors ([http://dx.doi.org/10.1107/S0907444911049833 Müller, Wang and Schulze-Briese (2012), Acta Cryst D68, 42]), but this should not be specific for Pilatus. | and thereby re-run the INTEGRATE and CORRECT steps. This has the advantage that the refined geometry parameters (from CORRECT) are recycled into INTEGRATE, which sometimes leads to better R-factors. It also results in the spacegroup's restraints on the unit cell parameters being used for the prediction of spot positions; these are therefore slightly more accurate. Fine-slicing of profiles has been found to be advantageous at least for Pilatus detectors ([http://dx.doi.org/10.1107/S0907444911049833 Müller, Wang and Schulze-Briese (2012), Acta Cryst D68, 42]), but this should not be specific for Pilatus. | ||
=== using the refined values for beam divergence and mosaicity for re-integration === | |||
If the beam divergence and mosaicity is fairly constant throughout the experiment, or there are few reflections on each frame to estimate these parameters from, then it might be beneficial to use the average values for beam divergence and mosaicity for the second integration. The values from the first integration can be found in INTEGRATE.LP, and the relevant two lines e.g, | |||
BEAM_DIVERGENCE= 2.067 BEAM_DIVERGENCE_E.S.D.= 0.207 | |||
REFLECTING_RANGE= 2.303 REFLECTING_RANGE_E.S.D.= 0.329 | |||
should be pasted into XDS.INP, and the INTEGRATE CORRECT jobs re-run (see [[Difficult datasets]]). This can be combined with the above optimization. | |||
=== Wilson outliers (aliens) === | === Wilson outliers (aliens) === | ||
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=== Optimizing the anomalous signal === | === Optimizing the anomalous signal === | ||
It | It may be helpful to increase WFAC1 from its default 1.0 to 1.5, to avoid rejection of the strongest Bijvoet pairs (this is not necessary when STRICT_ABSORPTION_CORRECTION=TRUE which is ''not'' the default). | ||
Read [[Tips_and_Tricks#SAD.2FMAD_data_reduction]] concerning STRICT_ABSORPTION_CORRECTION. | Read [[Tips_and_Tricks#SAD.2FMAD_data_reduction]] concerning STRICT_ABSORPTION_CORRECTION. | ||