Ice rings: Difference between revisions

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* Please see [[Wishlist#Would be nice to have]]: there's a list of additional (high-) resolution ranges one might want to exclude (in [[CORRECT]]).
* Since XDS version March 30,2013, one can use INCLUDE_RESOLUTION_RANGE and EXCLUDE_RESOLUTION_RANGE already in the IDXREF step. For the latter to be effective, the geometry should of course be rather accurate. The former may be used with an upper value of 4 for the IDXREF step to obtain indexing without ice rings. To process higher resolution data, the upper value then has to be modified for the DEFPIX INTEGRATE CORRECT step.  
* A currently possible way to prevent ice rings from spoiling the [[IDXREF]] step is to set "TRUSTED_REGION=0 X" for INIT, where X is calculated such that ice rings are excluded. Using Bragg's law and an approximation, we find that <br /> X = <math>\frac{Wavelength \cdot Distance} {4 \cdot NX \cdot QX}</math> should give approx. 4 Å cutoff, which should exclude all ice rings. <br /> Drawback: after successful indexing, INIT needs to be re-run with "TRUSTED_REGION=0 1.05" or so.
 
A potential pitfall: the above assumes that the direct beam position is near the middle of the detector.
* Please see [[Optimization]] for how to treat remaining ice reflections showing up as "aliens" in [[CORRECT.LP]].
* Please see [[Optimization]] for how to treat remaining ice reflections showing up as "aliens" in [[CORRECT.LP]].
* additional ice rings (beyond those in the detector templates) are at
    1.524 - 1.519
    1.473 - 1.470
    1.444 - 1.440
    1.372 - 1.368
    1.367 - 1.363
    1.299 - 1.296
    1.275 - 1.274
    1.261 - 1.259
    1.224 - 1.222
    1.171 - 1.168
    1.124 - 1.122
according to https://www.globalphasing.com/autoproc/ReleaseNotes/ReleaseNotes-autoPROC_snapshot_20170623.txt which cites Kumai, M. (1967). A study of hexagonal and cubic ice at low temperatures. Research Report 231, U.S. Army Materiel Command, Cold Regions Research & Engineering Laboratory, Hanover, NH.

Latest revision as of 13:43, 4 July 2017

  • Since XDS version March 30,2013, one can use INCLUDE_RESOLUTION_RANGE and EXCLUDE_RESOLUTION_RANGE already in the IDXREF step. For the latter to be effective, the geometry should of course be rather accurate. The former may be used with an upper value of 4 for the IDXREF step to obtain indexing without ice rings. To process higher resolution data, the upper value then has to be modified for the DEFPIX INTEGRATE CORRECT step.
  • Please see Optimization for how to treat remaining ice reflections showing up as "aliens" in CORRECT.LP.
  • additional ice rings (beyond those in the detector templates) are at
    1.524 - 1.519
    1.473 - 1.470
    1.444 - 1.440
    1.372 - 1.368
    1.367 - 1.363
    1.299 - 1.296
    1.275 - 1.274
    1.261 - 1.259
    1.224 - 1.222
    1.171 - 1.168
    1.124 - 1.122

according to https://www.globalphasing.com/autoproc/ReleaseNotes/ReleaseNotes-autoPROC_snapshot_20170623.txt which cites Kumai, M. (1967). A study of hexagonal and cubic ice at low temperatures. Research Report 231, U.S. Army Materiel Command, Cold Regions Research & Engineering Laboratory, Hanover, NH.

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