Re: [sdpd] Re: how to purchase a high resolution diffractometer

[Jaap Vente <jaap...@jade.mda.cinvestav.mx>]

The discussion is now should one buy a machine with or without primary
monochromater, or in other words without or with Kalpha2. 

In my experience based on Siemens D-5000, with a peakwidth of about
0.06deg at 30deg 2the, a Rietveld refinement on an 'ideal' material is
very much the same. The results are equally (dis)satisfying. However if
you have some anisotropic broadening, due to e.g. stacking faults, or
slight distortions, than  there is a real advantage of using Kalpha1 only.
Yes, you can believe your eyes at times to see immediate that a peak is
wider than it's neighbours. Kalp2 is than just a pain in the neck. The
negative point is you may get more problems with fluoresence, giving
horridly high backgrounds, but nicely low R-values. 
That is also one reason why we do not use only R-values. 
Stripping methods are NOT reliable, at least i have never seen one that
was!

I think that both methods have distinct advantages and disadvantages, and
it will boil down to personal preferences, which one to pick.



Best

Jaap


Jaap Vente
Cinvestav-IPN Unidad Merida
Departamento de Fisica Aplicada
Carretera Ant. a Progreso km 6
Apartado Postal #73 Cordemex
Merida, Yucatan, 97310
Mexico
Fax: +52 (9) 981 29 17
Tel: +52 (9) 981 29 60 ext 243/230
e-mail: jaap...@mda.cinvestav.mx
web: http://www.mda.cinvestav.mx/  


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