Questions about strain mapping

Hello,

Thanks a lot for creating the py4DSTEM package. I have been using it for strain mapping for a while and it's user-friendly. I have a couple of questions I wanted to ask. I am sorry if I am using the wrong channel to ask questions:

1. For calibrating the center positions of the braggpeaks, I used the "measure_origin" followed by "fit_origin" functions but I see strong residuals after the fitting. I tried all three fitting options ('plane', 'parabola' and 'bezier_two') and I get strong residuals with all three of them. I am wondering if it is ok to have large residuals and I can just continue with the process. Or should I try to create a custom function for every data depending on how the data looks? Could you please advise me on this?

2. I collected 4D STEM data with two different C2 aperture sizes (50 and 20). C2 50 gives more of diffraction disks and C2 20 gives diffraction spots. I am wondering if I should change the negative trench size for creating probe kernel for C2 50 vs C2 20? Is there a guideline as to how to decide the size of the negative trench for creating the probe kernel? Also, in general, is the bragg peak finding routine affected by diffraction spots vs disks? I am asking these questions because our strain values look vastly different for C2 20 vs C2 50. All other experimental parameters were kept the same.

Thanks in advance.

Start by reading the measure_origin and fit_origin entry points, then trace the probe-kernel and Bragg-peak-finding guidance for differing C2 aperture sizes. Done means providing project-specific guidance on interpreting fitting residuals, choosing negative-trench sizes, and explaining why strain values may differ between diffraction spots and disks.