Dear Matthew, For most of my work with electron diffraction, I used SHELXL for refinement (e.g. https://doi.org/10.1002/anie.201811318, https://doi.org/10.1107/ S2052252518000945, or http://www.dx.doi.org/10.1107/S2053273315022500). L Peng ("Electron atomic scattering factors and scattering potentials of crystals", Micron 30 (1999), 625-648) has published the parameters for electron scattering factors suitable for SHELXL. Peng used a1-a4, and b1-b4, i.e. c=0 in the Cromer-Mann-Parametrisation used in SHELXL. Normally I start with these parameters and fit the full Cromer-Mann-function to the calculated values from Int. Tables C, Table 4.3.1.1. with gnuplot. There is not a huge improvement compared to the published values,however, fitting manually has two advantages for me: - it is a control, as my gnuplot-script produces a PDF-file for the fit - I can fit against ionic scattering factors from Table Table 4.3.1.2
For the latter, you have to choose an appropriate low-resolution cut-off, as for ions, the behaviour at s=0 is not defined. I recommend reading Yonekura eta l., https://doi.org/10.1107/S2052252518005237 I can send you my current list of scattering factors in SHELX, the gnuplot script and a selection of PDF-plots if you like. For small molecules, SHELXL is certainly the program of choice. As additional information: Refmac5 uses the Mott-Bethe formula for the scattering factors. I could see not difference between the Mott-Bethe-formula (for non-ions, only as far as I understand) and the direct parametrisation, and I suggested to George Sheldrick to incorporate this in SHELXL as well. It is great to hear you are working on electron crystallography, too, as this might be additional motivation. Let me know in case you would like a copy of my list of scattering factors in SHELX format. Best regards, Tim On Monday, March 4, 2019 9:20:08 PM CET Whitley, Matthew J wrote: > Greetings all, > > > We have solved a small molecule structure using electron diffraction and > would like to refine the structure with SHELXL. Coming from a > macromolecular background, this is our first experience with SHELXL, and we > are not exactly sure how to proceed. The first thing to do seems to be to > provide SHELXL the appropriate electron scattering factors for 200 keV > electrons. Can someone suggest the best way to do this? Or, > alternatively, if anyone has used a different program to refine small > molecule structures determined by ED, we would be happy to hear about that > program too. > > > Thanks in advance for your advice. > > Matthew > > > --- > Matthew J. Whitley, Ph.D. > Research Instructor > Department of Pharmacology & Chemical Biology > University of Pittsburgh School of Medicine > > ######################################################################## > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 -- -- Tim Gruene Head of the Centre for X-ray Structure Analysis Faculty of Chemistry University of Vienna Phone: +43-1-4277-70202 GPG Key ID = A46BEE1A ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
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