Greetings,

I am analyzing some martensite/austenite in-situ phase transformation data with Topas academic 6, and I am currently having some troubles with the crystallite size (CS) and microstrain (MS). The results for these parameters either vary drastically, or the obtained error is very large. This is more evident in the austenite results.

As far as I understood, the double-Voigt approach assumes that both CS and MS can be obtained by the peak's deconvolution using a Gaussian and Lorentzian component.

However, in some old Topas 4.2 templates in my department, I found that the CS is evaluated only with the Lorentzian component, and the MS is evaluated only with the Gaussian part.

Therefore, I try to apply this approach, and I observed much more stable results than the Double Voigt. However, I never found any information supporting this kind of approach.

My question are:
-Does it make sense to evaluate each parameter with one deconvolution component?
Lorentzian -> CS
Gaussian -> MS

-If it does not make any sense to use a single component for each parameter, is there anything that I can do to reduce this instability in the CS and MS results?

To further evaluate these differences, I batch-process one set of data using three different templates.

1st Template (double Voigt approach -> CS and MS)

'e0MA=microstrain
prm maxStr_a = 1;
Strain_G(GS_a, 0.50000`_0.27653 min 1e-6 max=maxStr_a;) 'Lorentzian component
Strain_L(LS_a, 0.50000`_0.33755 min 1e-6 max=maxStr_a;) 'Gaussian Component
prm e0Ma = Voigt_FWHM_GL((GS_a), (LS_a)) 0.25(Pi/360); : 0.00179`_0.00077

'cry_MA=crystallite size
CS_L(CS_La, 82.81536`_113.12992 min 5 max 2000) 'Lorentzian component
CS_G(CS_Ga, 1921.96712`_2425283.23754 min 5 max 2000) 'Gaussian Component
prm cry_Ma = (1) / Voigt_Integral_Breadth_GL(1/(CS_Ga), 1/(CS_La)); : 52.87025`_326.26019

2nd Template (Lorentzian ->CS and Gaussian-> MS)

'e0MA_G = microstrain
prm maxStr_a = 1;
Strain_G(GS_a, 0.50000`_0.09516 min 1e-6 max=maxStr_a;)
'Strain_L(LS_a, 0.1 min 1e-6 max=maxStr_a;)
prm e0Ma_G = Voigt_FWHM_GL((GS_a), ) 0.25(Pi/360); : 0.00109`_0.00021

'cry_MA_L = crystallite size
CS_L(CS_La, 29.37136`_3.01216 min 5 max 2000)
'CS_G(CS_Ga, 20 min 5 max 2000)
prm cry_Ma_L = 1 / IB_from_CS( ,CS_Lt); : 66.39920`_2.34188

3rd Template (Gaussian -> CS and Lorentzian -> MS)

'e0Ma_L = microstrain only with Lorentzian
prm maxStr_a = 1;
'Strain_G(GS_a, 0.1 min 1e-6 max=maxStr_a;)
Strain_L(LS_a, 0.50000`_0.08756 min 1e-6 max=maxStr_a;)
prm e0Ma_L = Voigt_FWHM_GL( 0 , (LS_a)) 0.25(Pi/360); : 0.00109`_0.00019

'cry_Ma_G = crystallite size only with Gaussian
'CS_L(CS_La, 20 min 5 max 2000)
CS_G(CS_Ga, 30.05365`_4.68249 min 5 max 2000)
prm cry_Ma_G = 1 / IB_from_CS(CS_Ga, ); : 28.23352`_4.39891

Here is a comparison of the obtained results for crystallite size and microstrain. (I tried to upload an image)

I am a beginner with Topas and would appreciate any suggestions and comments. (sorry for the long post)

Best regards,
Antonio Silveira