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

[cockcroft...@gordon.cryst.bbk.ac.uk]

I basically agree with Robin Shirley's earlier comments. I would add that 
the transmission setup can be optimized further than we do here regarding 
resolution - our Bragg-Brentano setup has narrower peak widths than the 
equivalent capillary transmission setup, but that is our choice! :-) 
As usual there is a compromise between resolution and intensity, and our setup
is more for Rietveld refinement than say indexing. 

Having a choice of two diffractometers, it is clear that certain types of
experiment are done better on one than the other and vice versa. Routine
sample identification if usually better on the reflection setup, whereas
Rietveld work is nearly always better with the transmission geometry. Also
capillaries are easier to cool - routine with a liq. N2 cryostream, somewhat 
less routine with a liq. He cryostat. This is something you should consider 
when working with organic materials where the high-angle part of the
pattern may be wiped out by thermal motion at room temperature.

Jeremy Karl Cockcroft,
School of Crystallography,
Birkbeck College, University of London, 
United Kingdom.

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