py4dstem / py4dstem/py4DSTEM

Questions about strain and orientation mapping

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Description

Thanks very much for creating the very useful py4DSTEM package. I have a few questions about strain mapping and ACOM routines:

  1. I acquire my 4DSTEM data for strain mapping using C2 20 aperture (0.6 mrad semi convergence angle and 2.3 nm probe size FWHM). So, I see diffraction spots instead of disks. When I set template = None in the disk detection step during the data processing, the code is not detecting any spots at all. Should I change any of the filtering arguments such as minAbsoluteIntensity or minRelativeIntensity or subpixel when using template = None?

  2. I use the same CL and C2 aperture for all my experiments. So, I created one probe template by collecting a quick dataset from vacuum and use the same to detect spots for all my datasets. As of now, I saved the probe template as a tif image and load it back as kernel and pass it to template. Is it ok to do that? Or, is there a better way to save the probe template and reuse it?

  3. For ACOM routine, if my dataset has 2 polycrystalline materials, say W and Cu, in the field of view, how do I go about it? Do I run the ACOM routine for the entire dataset twice, one for each material? Also, that will give me separate orientation maps of Cu and W. Is there a way to combine them into one composite map?

  4. For ACOM routine of one material, after I get the orientation map, is there a way to measure the grain sizes? Are you planning to add that routine in the future? I am just curious.

py4DSTEM version: 14.9
Python version: 3.11.4

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Research direction

Start with the disk-detection entry point for template=None and the ACOM routine; the issue names no files or tests to run. Check how filtering arguments, reusable probe templates, multiple materials, composite orientation maps, and grain-size analysis are documented in py4DSTEM 14.9. Done means providing clear, version-specific answers or documenting any confirmed gaps.

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Assessment

Tech stack
python
Domain
data
Issue type
Documentation
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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