[GSAS-II] Query on Exporting Error Values for Size and Microstrain in GSAS-II

[Von Dreele, Robert B.]

Dear Luiz,
Your approach (refine one parameter & then refine the other) does not produce valid results or estimated standard deviations (sigmas). There is a significant difference in the functions for size and mustrain with respect to scattering angle so they should not be so correlated that they can't be refined simultaneously. One depends on 1/cos(theta) while the other is dependent on tan(theta). Unless your sample is "nanocrystalline" (size << 1 micron) the dominant broadening is almost invariably due to mustrain & you should refine accordingly. If you want to explore this, set size to a few fixed values (< 1 micron) & refine just mustrain. NB: for laboratory instruments, size >1 micron is meaningless as that size is effectively infinite for diffraction.
Bob
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From: GSAS-II <gsas-ii-bounces at aps.anl.gov> on behalf of Luiz Felipe Pompermaier via GSAS-II <gsas-ii at aps.anl.gov>
Sent: Monday, December 16, 2024 12:21 PM
To: Luiz Felipe via GSAS-II <gsas-ii at aps.anl.gov>
Subject: [GSAS-II] Query on Exporting Error Values for Size and Microstrain in GSAS-II

Dear GSAS-II Community, I hope this message finds you well. I would like to know if there is a way to export the error (sigma) associated with the size and microstrain values to the .lst file after completing a refinement. To provide some context: 
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Dear GSAS-II Community,

I hope this message finds you well.

I would like to know if there is a way to export the error (sigma) associated with the size and microstrain values to the .lst file after completing a refinement.

To provide some context: given the strong correlation between size and microstrain, I avoid refining them simultaneously. Instead, I refine one parameter at a time, alternating between them a few times, and then disable the refinement flags once I achieve satisfactory values.

However, this approach presents a challenge: by removing the refinement flags, I lose the sigma values associated with these variables, as they are no longer being actively refined. I would like to preserve the final sigma values in the .lst report.

Is there a way to achieve this within GSAS-II? Alternatively, would you recommend revisiting my refinement strategy?

Thank you in advance for your time and assistance.

Best regards,
Luiz Felipe Pompermaier
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