dtprocess on-line help

Copyright (c) 1997 Molecular Structure Corporation

Strategy: Determine a suitable scan rotation for data collection.

The Strategy menu prepares a dtstrategy command and runs it.
  1. Select a header from the top list. Usually this is dtrefine.head.
  2. Set the menu options described below.
  3. Select Run strategy
  4. View the dtstrategy log file.

Strategy menu options

Search rot start, end
Sets the range of reflections to predict and search for the best solution. For higher symmetry spacegroups, you may reduce the range drastically to save time.
Search resolution
Sets the resolution of reflection to predict and search for the best solution. Remember that low resolution reflections may be blocked by the beam stop, while high resolution reflections may be limited by the detector swing or corners. To save time, you may wish to find a preliminary strategy with a lower resolution range, then use the full range. A range of 0, 0 indicates the resolution to the EDGE (not corner) of the detector.
Min % completeness
The minimum acceptable percent completeness for a solution.
Max search rot range
The maximum allowed rotation range for a solution. No solution will have a range larger than this, even if the Min % completeness criteria is not met.
Cell length scale
Scale factor to apply to unit cell lengths. If this is less than 1, then prediction and testing for a solution are faster, but approximate. The number of reflections presented in the dtstrategy results are scaled appropriately if this value is less than 1 to reflect the true number of reflections involved.
Previous refs
If set, a previous reflection list specified here is loaded and retained in all completeness calculations (e.g. dtstrategy.ref or dtintegrate.ref. Thus, you may combine different scans to get the best completeness, or fill in data missing from a scan.
Predicted refs
If set, a predicted reflection list specified here is read in and no predictions are done. However, only reflections in this list which pass the Search rot start, end and Search resolution criteria are used. This option is useful if you have previously predicted a large rotation range with the Predict menu and want to save time when running several scenarios.
List params
If set, the -list option is set for dtstrategy.
Write reflns
If set, writes the reflections in the solutions to dtstrategy.ref. This file is suitable for input to a subsequent Strategy run as a Previous refs file.

More info

The Strategy tool has 4 principle criteria that must be specified:

  1. Rotation limits
  2. Resolution limits
  3. Completeness
  4. Max allowed range

You can used the tool to give you the range that fulfills your completeness criteria, the best start and end for a given max range, or the completeness of a given range.

For speed, set the Cell length scale to 0.5 or less, limit your resolution range. When you have narrowed down a scan range, set the Cell length scale back to 1 and the resolution to the desired range.

Example 1: What is the best 50 degree scan possible?

  1. Set the max allowed range to 50.
  2. Set the Min % completeness to 101.
  3. Select 'Run strategy'

Example 2: What is the completeness of a given scan?

  1. Set the rotation start and end of the desired scan.
  2. Set the Min % completeness to 101.
  3. Set the max allowed range to 1000.
  4. Select 'Run strategy'