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Re: [sdpd] Fullprof2k Problem

>ps: I dont know how to use Pearson VII function (Npr=6), the program 
>alway said that "Pearson VII M-value unacceptable!"
>Thank you!
>  
>
.........
>>The starting value should be higher than 1.0 (the typical value of
0.5 
>>for the pseudo-voigt causes the above error message).
.........

This recommendation is valid for pseudo-voigt, but not for Pearson VII.
The Pearson shape parameter M in Fullprof is calculated as:

M = Shape1 + 100* X / 2Theta + 10000* Y / (2Theta)**2

and M should be higher than 0.6 for all 2Theta values, otherwise the
message "Pearson VII M-value unacceptable!" appears.
When using Pearson VII, at the initial stages it is better to refine
only Shape1 (starting from Shape1=1.5) and fix the parameters X=Y=0. At
the final stages X and Y may be also refined but with caution.

Best,
Leonid



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