Re: [sdpd] Relationship between Site Occupancy Factor with Bond Length and Bond Angle

[Armel Le Bail <alb...@cristal.org>]

Hello,

>I was trying using high energy ball milling on Zinc Oxide. I was trying to 
>refine site occupancy of the Zn and O. However, the Rwp would decrease but 
>the Rb would increase for the ball milled ZnO. Does it mean a false minima 
>occuring?

I tried (small energy) ball milling on ZnO in 1983-1985. Not really
published. There is a report corresponding to a Siemens meeting
in Grenoble (France) - in French...:
http://www.cristal.org/postscript/siemens-1985.pdf
You will see some figures of the powder patterns (well crystallized
and ball milled) and you can compare with your own patterns. There are
also some results about NiF2, W, Ni(OH)2.

Well, no change at all was observed after ball-milling: nothing on
the cell parameter, nothing on atom occupancy, nothing on
atomic coordinates, etc.

If your powder patterns show more line broadening than mines,
then, how do you estimate the background (do you use a zero-background
sample holder ?), how do you cope with line broadening, is your fit 
satisfying ?

Be prudent before to conclude to any variation (in atom occupancy or
something else).

Best regards,

Armel



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