Error using Powder diffraction pattern

[kambiz shojaee]

Hi,

First of all, I have to admit  that VESTA is one of the best visualization software I ve ever used. 

When I use Powder diffraction pattern for a POSCAR file, I encounter with this message:

NPAT = 24

The above value of NPAT is not allowed. 

RIETAN stoped with an error. Check the output file, "POSCAR.lst"

I really appreciate any help. 

[Philip Howie]

This issue has been addressed in the following thread:
https://groups.google.com/forum/#!topic/vesta-discuss/8xhgYRhxL7I

Hope that helps,

Philip

[kambiz shojaee]

Hi Philip,

Thanks, yes it helped :)

I really appreciate it. 

[kambiz shojaee]

Hi again,

I was also wondering if your could help me understanding NPRINT keyword. 

The manual says "A list of reections output in *.lst if NPRINT > 0 provides us with a variety of information about reflections included in the simulated pattern."

I NPRINT = 2 in the template files I see no detailed information about the Miller indices and peaks. but put Where are these output data? 

Thanks a lot 

[Philip Howie]

When I run RIETAN and look at the .lst output file, I see a section headed

    *** Summary of possible reflections (based on the user-supplied parameters) ***

which lists the peaks with Miller indices, d spacings (and errors), 2theta values, structure factors, etc.

[kambiz shojaee]

Thanks man, you r a savior.

Cheers

[kambiz shojaee]

Hi again :)

I m getting very similar patterns using Rietveld analysis for Fe3O4 and CoFe2O4, tough they have a different symmetry. 

Should I change any parameters in template file when symmetry is changing ? 

I really appreciate it. 

Regards 

[Philip Howie]

What do you mean when you say they have a different symmetry?  The data I've found for CoFe2O4 all suggest that it has exactly the same symmetry as Fe3O4.  Indeed, it's exactly the same structure, but with the Co atoms disordered across one or both of the Fe sites.

In this case, any change in the diffraction pattern will be very small.  The atomic scattering factor scales roughly as the atomic number, Z.  Since Fe and Co are adjacent in the periodic table, their atomic scattering factors are very similar.  Distinguishing between the two diffraction patterns experimentally will require very good data, if it is actually possible!

Hope that helps,

P

[kambiz shojaee]

hi,

you r awesome man. 

Yes,,they are usually mentioned with the same symmetry as Fd3m, however, at low temperature, they go under symmetry transition. usually, it is a tetragonal distortion. Fe3O4 may also show a Imma or CM symmetry. Supposedly, Imma symmetry should show a different XRD reflection compared to a cubic one.  

I got my answer from your post, anyway. thanks man. you r the best.