XDS.INP
XDS.INP is a user-provided file that is read by XDS. Each line consists of one or more <keyword>=<parameter(s)> pairs.
Complete documentation is at http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xds_parameters.html .
Templates for various detectors are at http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xds_prepare.html .
The most important keywords to get data reduction running
These keywords have no default parameters and must be given with the correct values.
The values may be obtained from logfiles of the beamline software, your notes, or (for many types of frames) from the headers of the frames (using 'strings <filename>|more'). A good way to retrieve them is by using MOSFLM.
A minimal XDS.INP needs at least these keywords and their parameters:
ORGX ORGY - in pixels The most critical parameters for a successful data reduction . See Obtaining ORGX ORGY
DETECTOR_DISTANCE - in millimeters
OSCILLATION_RANGE - in degrees
X-RAY_WAVELENGTH - in Angstrom
NAME_TEMPLATE_OF_DATA_FRAMES - path and name of frames, with wildcards for numbers
DATA_RANGE - numbers of frames to be reduced
BACKGROUND_RANGE - same for initial calibration purposes
DETECTOR NX NY QX QY - for a list of supported detectors and possible geometries, see http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xds_parameters.html#Table%20of%20supported%20detectors .
DIRECTION_OF_DETECTOR_X-AXIS - often 1 0 0
DIRECTION_OF_DETECTOR_Y-AXIS - often 0 1 0
INCIDENT_BEAM_DIRECTION - often 0 0 1
ROTATION_AXIS - often 1 0 0 at a synchrotron
Keywords for space group assignment
- If you know the space group and unit cell parameters of your crystal in advance you just need these two keywords:
- If you want to assign a space group and unit cell parameters to a crystal you most probably need this keyword as well:
The way how to determine a space group (and unit cell parameters) is described in space group determination.
Keywords which affect the quality of data reduction
REFINE(IDXREF) - The defaults (REFINE(IDXREF)=DISTANCE BEAM ORIENTATION CELL AXIS i.e. refine everything) are OK, but only if COLSPOT has seen all (or rather, a significant fraction of the) frames. If only a small SPOT_RANGE was used (which is not the best way, but possible), one should use REFINE(IDXREF)= AXIS BEAM ORIENTATION CELL . (The next thing to omit would be AXIS)
REFINE(INTEGRATE) - The defaults (REFINE(INTEGRATE)=DISTANCE BEAM ORIENTATION CELL) could be modified by omitting DISTANCE, because one should assume that the distance is constant. Furthermore, by fixing the distance one can better see from the results of the refinement whether the cell parameters are stable, or whether they change due to radiation damage.
REFINE(CORRECT) - The defaults (REFINE(CORRECT)=DISTANCE BEAM ORIENTATION CELL AXIS i.e. refine everything) are OK
MINIMUM_ZETA - the default of 0.15 is rather on the safe side. A lower value increases completeness.
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Keywords whose default parameters rarely need to be changed
MAXIMUM_NUMBER_OF_PROCESSORS - speeds up XDS by use of several (e.g. 2-4) CPUs within a single machine.
MAXIMUM_NUMBER_OF_JOBS - speeds up XDS by chopping the DATA_RANGE into pieces, and feeding each piece to a new process. That process may run on the local machine, or a different one (but this needs to be configured by the system administrator). Unless you know what you are doing, use MAXIMUM_NUMBER_OF_JOBS=1 - or at least don't set both MAXIMUM_NUMBER_OF_PROCESSORS and MAXIMUM_NUMBER_OF_JOBS to values >1!
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What can go wrong with this file?
The most important pitfalls are:
- Lines longer than 80 characters are truncated silently (FIXME: is this still true?). This happens most often with the NAME_TEMPLATE_OF_DATA_FRAMES keyword line, because the path to the directory with the frames may be long. Fix: use a symlink to the directory with the frames.
- Error due to omitting the "=" directly after the keyword (i.e. having an intervening blank).
- There may be decoding errors in the parameter which may lead to obscure error messages. E.g., see what happens if you provide only one cell parameter instead of six!
Written by --Kay 14:44, 8 November 2007 (CET)