Synthetic data sets are useful to learn how to process data. You can input the experimental parameters you will use in your actual experiment and your actual sample. The software to do so is PolyXSim

PolyXSim -i input_file (.inp or .ini)

Input file can include a collection of parameters. Information on the input parameters can be found here https://sourceforge.net/p/fable/wiki/PolyXSim%20-%20input/

Here are input files for simulating an experiment at the P02.2 beamline in PETRA

• Wavelength is 0.289 Å
• Detector is a Perkin-Elmer with 2048×2048 pixels, 200 μm pixel size in both directions, 400 mm from the sample. No tilt, no messing with detector orientation.
• Data collected over an range of Δω = [-28°;+28°] in steps δω = 0.5°.

Grain information

• 10 grains of post-perovkite
• random crystal orientations
• no strain
• randomly placed in a box of 10 x 10 x 10 μm³
• grains of 1 μm grain size in average with a minimum grain size of 0.5 μm and a maximum size of 1.5 μm
• no background noise
• very sharp peaks

The full input file is here simu-ppv-basic.inp

This second input file is the same experiment as previous but

• peak shapes are set to Gaussian with 0.02° spread in 2θ, 0.5° in η and 0.5° in ω
• A background with noise.

This second dataset is more difficult to process. You will really need to work on your background to get it to work.

The full input file is here simu-ppv-bg.inp.

Computations are much longer. Expect 1 minute per image. 2 hours for 112 images.

Here are typical errors that we bumped into

• Be careful of the intensity (beamflux). Should be in the order of 10¹⁵-10¹⁷
• Check the name of the parameter for the space group number (sgno) or space group symbol (sgname).

There are a number of possible output files from this procedure. Possible output files include:

• edf: diffraction images, with a header including the omega angle. Be careful, you might be generating gigabytes of data!
• tif: diffraction images in TIFF format. Be careful, you might be generating gigabytes of data!
• flt - peaks, as you would get them from a peak searching routine and that can be loaded in ImageD11.
• gff - a file containing grain information, 1 grain on each line
• gve - a list of g-vectors, as you should see them in an experiment. The peaks are transformed into scattering vectors (g-vectors). This file can be used for indexing in either GrainSpotter or ImageD11- index.
• ini - an sample input file for indexing with GrainSpotter. Using the .gve file is written. It will then be possible to try the GrainSpotter indexing program immediately.
• ubi - a list of the UBi matrices of the simulated grains. Grain orientations as inv(U*B).
• ref - reflection files (one per grain) having all the information about the reflections.
• par - the input parameters for PolyXSim written in the par format of for ImageD11.