What will be the intial value of occupancy that has been used during Reitveld refinement of TIO2-rutile structure?

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Christophe Lefevre

If you work with Fullprof, the starting parameters for rutile are the following:

P 42/m n m

Apurva Gangrade

Thanks Christophe, I am working on MgH2 (rutile), so will it be same for MgH2 and why did you take Biso=0.

Regards

It's just the starting file. During my refinement, I have also fitted Biso (close to 0.8 after refinement if I well remember)

best wishes,

Thanks Christophe, can you please explain me why the occupancies are .0125 and .25. if possible. I didn't understand there meaning.

Thanks & Regards,

Apurva

In Fullprof, the occupancy factors are defined by : (multiplicity of the site)/(multiplicity of a general position).

- Rutile crystallizes in the space group #136 = P42/mnm. The general position (x,y,z) of this sg has a multiplicity = 16.

- Ti is located at the position (0,0,0) ; according to the Int. table of crystallography, its multiplicity is 2. It's occupancy is thus 2/16 = 0.125

- Using the same reasoning, O is at the position (x,x,0). it's multiplicity is therefore 4 and then it's occupancy is 4/16 = 0.25

Best wishes,

Thanks a lot.

Dear Christophe,

What are the steps that should be followed in refinement if there is small contribution of other phases? During refinement of three phases in Fullprof i.e. MgH2, Mg and MgO together, the program shows error ("some scattering coeffients not found"). Can I refine all of them separately and find their weight percentage or refine them alltogether? Please suggest me.

Regards,