Re: [sdpd] V4+

[Lubomir Smrcok <uachsmrk...@savba.sk>]

My question :
this is a "powder" group, isn't it ? I wonder if there is any SIGNIFICANT
difference if you use a combination of i) powder (x-ray, synchrotron)
data and ii) a scattering curve for an ionized atom instead of a neutral
one. This could possibly work for a high quality single crystal data, but
for powders ? Please, don't tell me that with an ionized atom Rwp drops
for e.g 3%, this is hardly an argument.
Please, tell me that using of such a scattering curve has made your
refined interatomic distances more accurate, etc. ... give me an example,
please.

Best wishes,
Lubo Smrcok


On Mon, 13 Dec 2004, Armel Le Bail wrote:

>
>
> >I suspect that modeling the scattering from V(IV) in a compound using a gas
> >phase V4+ scattering factor is not a good approximation to reality for most
> >solids. Does anybody want to comment further on this?
>
> I would ask for another comment...
>
> Some mean atomic scattering factors for chemically
> significant ions are lacking in the International Tables
> for Crystallography.
>
> The most obvious one is that of O2-.
>
> Is there any good reason for continuing to not insert
> the X-ray scattering factor of O2- into the International
> Tables for Crystallography ? Anyway, people
> refining oxide structures can find it elsewhere. So, is
> that the decision of a very influent person or of a group
> of influent persons in charge of the Tables ?-). Or do they
> have forgotten it ? Strange isn't it ? Given that the scattering
> factor for O1- is provided, and probably not used by many
> crystallographers.
>
> Armel
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>


------------------------ Yahoo! Groups Sponsor --------------------~--> 
Make a clean sweep of pop-up ads. Yahoo! Companion Toolbar.
Now with Pop-Up Blocker. Get it for free!
http://us.click.yahoo.com/L5YrjA/eSIIAA/yQLSAA/UIYolB/TM
--------------------------------------------------------------------~-> 

 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/sdpd/

<*> To unsubscribe from this group, send an email to:
    sdpd-unsubscribe...@yahoogroups.com

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/