Brian,
That's right. The only reason to use O2- form factor is to model disordered
water molecules (e.g. when H atoms cannot be located) since O2- has the
same number of electrons as H2O. BTW: I saw somewhere extrapolated form
factor for H2O which would be even better for this purpose.
Peter
....................................................................
Peter Y. Zavalij, PHD
Director - X-ray Crystallographic Center
University of Maryland,
College Park, MD 20742
On Tue, Feb 21, 2023 at 1:11 PM Toby, Brian H. <t...@anl.gov> wrote:
> I am going to make the comment that (A) neutral atom form factors are
> probably closer to the actual electron distribution in most materials where
> there is significant covalent bonding (~= almost everything) and (B) even
> if that were not true, the difference between O, O1- and O2- is probably
> pretty minor for powder diffraction, so the choice does not matter. Except
> at very low angle, the form factor curves are just about the same for
> ionized atoms as neutral ones. (This is understandable since ionization
> only affects the outer shell electrons.) So, other than a small change in
> the first reflection or two, easily swamped by experimental artifacts, one
> just does not see any difference.
>
> I personally use only neutral atom form factors.
>
> Brian
>
>
> On Feb 21, 2023, at 4:10 AM, Matthew Rowles <rowle...@gmail.com> wrote:
>
> Thanks all
>
> It looks like fat fingers all around!
>
> W&K doesn't contain O2-, does contain O-
> RR&G _does_ contain O2-, doesn't contain O- (every version of the
> waasameir data I've found online has this typo, so I'm pretty sure they're
> all the same file.)
>
> Now just to cross-check the data to see if they're the same (and
> actually _read_ the papers)
>
> I'll also check out the other papers, and start looking for some N3-.
>
> Thanks
>
>
> Matthew
>
>
>
>
>
>
>
>
> On Tue, 21 Feb 2023 at 17:44, Kern, Arnt <arnt.k...@bruker.com> wrote:
>
>> Hello Daniel, hello all!
>>
>>
>>
>> Daniel, you are right. I just obtained the Hovestreydt paper, he actually
>> published a 9 coefficients representation.
>>
>>
>>
>> My apologies!
>>
>>
>>
>> Cheers,
>>
>>
>>
>> Arnt
>>
>>
>>
>>
>> -Bruker Confidential-
>>
>> *Von:* rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> *Im Auftrag
>> von *Többens, Daniel
>> *Gesendet:* Dienstag, 21. Februar 2023 09:58
>> *An:* rietveld_l@ill.fr
>> *Betreff:* Re: scattering factor for O2- ?
>>
>>
>>
>> Hello Arnt,
>>
>> I believe you are probably mistaken. The file at GitHub cites at the
>> source of most of its scattering factors either the paper of Waasmaier &
>> Kirfel ("New Analytical Scattering Factor Functions for Free Atoms and
>> Ions", D. Waasmaier & A. Kirfel, Acta Cryst. A 95) or the International
>> Tables, with the sole exception of "Fit for O1- based on the tabulated
>> values of Table 2 (D. Rez, P. Rez & I.Grant, Acta Cryst. (1994), A50,
>> 481-497)."
>>
>> This is most certainly a typing error, as neither of the former two
>> contains values for O2-, while the paper of Rez does not contains values
>> for O2-, but not for O1-. I would be very surprised if the values there
>> were not fitted to the table of Rez.
>>
>> Just for the sake of completeness, there are at least two more papers
>> with scattering factors for O2-:
>>
>> Schmidt, P.C., K.D. Sen, and A. Weiss, The Spherical Crystal-Potential
>> and Physical-Properties of Ions in Crystals - a Hf-Calculation for the
>> 10,18, and 36-Electron Closed Shell Ions of X-Ray-Scattering Factors,
>> Diamagnetic Susceptibilities, and Dipole Polarizabilities. Berichte Der
>> Bunsen-Gesellschaft - Physical Chemistry Chemical Physics, 1980. 84(12): p.
>> 1240-1251.
>>
>> Azavant, P. and A. Lichanot, X-Ray-Scattering Factors of Oxygen and
>> Sulfur Ions - an Ab initio Hartree-Fock Calculation. Acta Crystallographica
>> Section A, 1993. 49: p. 91-97.
>>
>> Good Luck to everyone out there,
>> Daniel Többens
>>
>> Am 21.02.2023 um 07:52 schrieb Kern, Arnt:
>>
>> Hi Matthew,
>>
>>
>>
>> I am pretty sure, this is
>>
>>
>>
>> “On the atomic scattering factor for O2-“
>>
>> E. Hovestreydt
>>
>>
>>
>> Acta Cryst. (1983). A39, 268-269
>>
>> https://doi.org/10.1107/S0108767383000550
>>
>>
>>
>> I don’t have the paper at hand, unfortunately.
>>
>>
>>
>> Cheers,
>>
>>
>>
>> Arnt
>>
>>
>>
>>
>>
>>
>> -Bruker Confidential-
>>
>> *Von:* rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr>
>> <rietveld_l-requ...@ill.fr> *Im Auftrag von *Matthew Rowles
>> *Gesendet:* Dienstag, 21. Februar 2023 01:38
>> *An:* RIETVELD_L Distribution List <rietveld_l@ill.fr>
>> <rietveld_l@ill.fr>
>> *Betreff:* scattering factor for O2- ?
>>
>>
>>
>> **EXTERNAL EMAIL**
>>
>> Hi all
>>
>>
>>
>> I've been looking at atomic scattering factors recently, and in
>> particular, the 11-coefficient parameterisation by Waasmaier and Kirfel [1].
>>
>>
>>
>> In their paper, they give a parameterisation for O and O-, but in tables
>> I can find online (eg libdiffpy/f0_WaasKirf.dat at master ·
>> diffpy/libdiffpy (github.com)
>> <https://github.com/diffpy/libdiffpy/blob/master/src/runtime/f0_WaasKirf.dat>),
>> there is also an entry for O2-.
>>
>>
>>
>> Does anybody know where this came from?
>>
>>
>>
>> Thanks
>>
>>
>>
>> Matthew
>>
>>
>>
>>
>>
>> [1] D. Waasmaier & A. Kirfel, New Analytical Scattering Factor Functions
>> for Free Atoms and Ions for Free Atoms and Ions, Acta Cryst. (1995). A51,
>> 416-413
>>
>>
>>
>>
>>
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