Hi Matt, I include below three references in which we demonstrate the inadequacies of the oxygen form factor used by powder diffraction software (top two refs) and by single crystal diffraction software (last ref).
In both the powder and the single crystal work, it was found that there were clearly resolvable differences between the structures determined using X-ray data and neutron data indicative of an error in the O2- form factor of 2 – 3 %. For the single crystal studies on LiFePO4, the full set of XRD data gave a structure different from the neutron result, but limiting the X-ray refinement to the low d-spacing data which has minimal contributions from the valence electrons led to excellent agreement with the neutron data. Similarly, the powder neutron data on a series of Li(Ni/Mn/Co)O2 samples clearly showed one dominant defect was present, but the X-ray data diverged. However, our analysis using the f* methods that we developed showed that the difference could be attributed to the oxygen site in the x-ray data contributing more scattering than would be expected for a 100% occupied site, again suggesting a problem with the form factors. We attribute this to the electron cloud in actual materials being non-spherical (as was clearly observed both in our single-crystal X-ray studies of LiFePO4 and the earlier charge density studies of others), in contrast to the results obtained for the gas phase quantum calculations used to obtain the x-ray form factors. Our overall conclusion was that modern diffraction techniques methods are now sensitive enough to make clear the limitations in the classic x-ray form factors, and that better calculations done with improved methodologies are necessary to overcome these limitations. So perhaps worrying about the details of old quantum calculations is less important since they cannot account for the non-spherical electron densities of atoms participating in bonds. Best wishes, Peter ---------------------- L. Yin, Z. Li, G. Mattei, J. Zheng, W. Zhao, F. Omenya, C. Fang, W. Li, J. Li, Q. Xie, E. Erickson, J.-G. Zhang, M.S. Whittingham, Y.S. Meng, A. Manthiram, and P. Khalifah, “Thermodynamics of anti-site defects in layered NMC cathodes: systematic insights from high-precision powder diffraction studies”, Chem. Mater., 32, 1002-1010 (2019). [Freely available ACS "Editor's Choice" manuscript, January 30, 2020] https://doi.org/10.1021/acs.chemmater.9b03646 L. Yin, G. Mattei, Z. Li, J. Zheng, W. Zhao, F. Omenya, C. Fang, W. Li, J. Li, Q. Xie, J.-G. Zhang, M.S. Whittingham, Y.S. Meng, A. Manthiram and P. Khalifah. “Extending the limits of powder diffraction analysis: diffraction parameter space, occupancy defects, and atomic form factors.” Rev. Sci. Instrum. 89, 093002 (2018). https://doi.org/10.1063/1.5044555 Y. Janssen, D. Santhanagopalan, D. Qian, M. Chi, X. Wang, C. Hoffmann, Y. S. Meng, and P. Khalifah, “Reciprocal Salt Flux Growth of LiFePO4 single crystals with controlled defect concentrations”, Chem. Mater., 25, 4574-84 (2013). https://doi.org/10.1021/cm4027682 Professor Chemist Dept. of Chemistry Dept. of Chemistry Stony Brook University Brookhaven National Laboratory Stony Brook, NY 11794-3400 Upton, NY 11973-5000 Office: 447 Grad. Chemistry Office: Bldg 555, Rm 340 Phone: (631)632-7796 Phone: (631)344-7689 Fax: (631)632-7960 Fax: (631)344-5815 From: rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> On Behalf Of Matthew Rowles Sent: Tuesday, February 21, 2023 5:10 AM To: Kern, Arnt <arnt.k...@bruker.com>; daniel.toebb...@helmholtz-berlin.de Cc: rietveld_l@ill.fr Subject: Re: scattering factor for O2- ? 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<mailto: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<mailto:rietveld_l-requ...@ill.fr> <rietveld_l-requ...@ill.fr<mailto:rietveld_l-requ...@ill.fr>> Im Auftrag von Többens, Daniel Gesendet: Dienstag, 21. Februar 2023 09:58 An: rietveld_l@ill.fr<mailto: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<https://urldefense.com/v3/__https:/doi.org/10.1107/S0108767383000550__;!!P4SdNyxKAPE!H8jPgsEJu2H42SSN6XheBqyaqWae-e-mV94gG_f-W3PGKfcWkAPK6T5NA9tsnPEd_C0giQ9ENrXAnCQ$> I don’t have the paper at hand, unfortunately. Cheers, Arnt -Bruker Confidential- Von: rietveld_l-requ...@ill.fr<mailto:rietveld_l-requ...@ill.fr> <rietveld_l-requ...@ill.fr><mailto: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><mailto: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). 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