Le Mardi 5 Mars 2019 10:41 CET, "Roversi, Pietro (Dr.)" <pr...@leicester.ac.uk> a écrit:
Many years ago I did teaching on diffraction by illustrating the major aspects of crystal structure determination with 2D crystals on 24x36 films. The crystal was an 80x60 repeats of the famous Einstein's tongue and MIR was illustrated with "beauty spots" added on Einstein's face. You can have a look to the attached diffraction image and to the little article in the IUCr newsletter on teaching, June 2006: https://www.iucr.org/resources/commissions/crystallographic-teaching/newsletters/1 Two remarks: First, unfortunately, the web site indicated in the article is essentially "dead" (but not completely) due to license problems with WebMathematica. Second, it is mentioned in the article that Friedel's law was significantly violated and that this was due to bad alignment of the negative film in the optical diffractometer. I'm no more sure that this is exact and I am wondering whether this could be due to a much more interesting effect of "anomalous diffraction" due to different optic lengths within the negative resulting from different amounts of reduced silver. (Does anyone has an idea about that?). If this were true, then on could imagine solving the Einstein's crystal structure, not only by MIR as shown initially, but also by SAD, and this would be very interesting. I long thought that I should come back to this teaching problem, but I never did it. Who knows: someone else could be interested... I would be very glad of sending you some "2D Einstein's tongue crystals" for your teaching. All the best Philippe Dumas > Dear all, > > I'd like to purchase slides with diffraction gratings for educational > purposes. > > Ideally, to be used with a visible-light laser pointer. > > And: with 1D and 2D patterns, of variable repeats - so as to be able to > illustrate the effect on the spacing in reciprocal space, as it were. > > I am looking online but not having much joy. > > Can anyone recommend a good provider to purchase from? > > Thank you! > > Pietro > > > > Pietro Roversi > > LISCB Wellcome Trust ISSF Fellow > > https://bit.ly/2I4Wm5Z > > > Leicester Institute of Structural and Chemical Biology > Department of Molecular and Cell Biology, University of Leicester > Henry Wellcome Building > Lancaster Road, Leicester, LE1 7HB > England, United Kingdom > > Tel. +44 (0)116 2297237 > > > ######################################################################## > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
DiffractionEisteinTongue.pdf
Description: Adobe PDF document
