Dear Morteza Tahmasebi Yamchelou,

You move the cursor until the background match with the minimum of the curve and you click on "Append Background as a scan"

Best regards.

Yassine El Khessaimi

Dear Yassine,

Many thanks for your answer. when I do so, i.e., when I move the background line to the lowest part of the main curve, I get 100 percent crystallinity which is unrealistic. Would you please tell me in more details what you mean?

Best

We need to be careful with the background treatment. The software-set thresholds for treatments such as the background subtraction are usually the best choices (so you immediately click "background subtracted"). On the other hand, I find the new EVA much worse in terms of the interface than the previous one...

What do you mean by 100% crystallinity? Do you calculate it somehow in EVA? I'd strongly encourage you to use TOPAS (or similar software) to calculate the degree of crystallinity. There you treat the background with more sophisticated curves (Chebychev polynomials with varying degrees and 1/x functions possible), but for each crystalline substance you can also maneuver with the CrystalSize in either Lorentzian or Gaussian peak shape description - this allows to avoid the sofware mixing up the background and the low-crystalline phases.

Cheers,

Luke Kruszewski

@Łukasz Kruszewski

Dear Lukasz,

There is a built-in option in refreac.eva which computes the crystalline and amorphous content of your powder sample. When you reduce the curvature in the background adjustment the crystalline percentage increases. I want to compute the exact amorphous content of my clay sample, but this value is very sensitive to the background noise and I want to know when the computed value is quite reliable. I will try to use the software you introduced, TOPAS, and see how the result changes.

Best,

Hi. That is interesting - I didn't know that...

However, I wouldn't use EVA to the crystalline/amorphous content calculation, but actually the issue is only when you want to calculate the contents of the particular crystalline species (EVA would then base on their intensities only, while the true content is dependent on both the intensity and also reflection shape). In TOPAS you introduce structure information (if there are CIF files for the particular compound, to be found, e.g., in the American Mineralogist Crystal Structure Database, or Crystallography Open Database, or elsewhere accessible via google) or "hkl phase" (if a structural model for the substance in question is nonexistent), while the "hump" marking the amorphous phase(s) are introduced by inputting the so-called Peaks Phase(s) (by pressing F3). After performing the Rietveld refinement, you can go to Miscellaneous --> Degree of Crystallinity --> Calculate D. of C.

I hope this helps you anyhow.

Have a nice week,

Łukasz Kruszewski