Dear Rietvelders, I have had a number of enquiries about how to join the totalscattering mailserv. In case anyone else is interested I am reproducing the instructions below (for the others, sorry for the spam): To subscribe send an email to [EMAIL PROTECTED] with the line "subscribe totalscattering" (without the quotes) in the body text. You will then receive a welcome message with instructions for using the list-serv.
As I mentioned in the previous email, the diffpy-users google group is currently more active for discussions of a PDF nature. Though strictly speaking, it is a discussion forum for people using the PDFgui modeling software, there are some discussion threads of a more general nature. You can join, or just browse, at the following link: http://groups.google.com/group/diffpy-users Again, sorry for the spam. S On Mon, Jul 28, 2008 at 12:35 PM, Simon Billinge <[EMAIL PROTECTED]> wrote: > Dear Ling, > > This is more appropriately answered at the totalscattering maillist: > [EMAIL PROTECTED] > > I will also post it to the diffpy-users google group in case someone > familiar with that list wants to chime in. > > Simon Billinge > > On Mon, Jul 28, 2008 at 11:03 AM, Yang, Ling <[EMAIL PROTECTED]> wrote: >> Dear All, >> >> There must be some problem with the mailing list since all my emails didn't >> get through. Hope this one will pass. >> >> Stimulated by the topics on pair distribution functions, can I ask some >> questions here about PDF analysis? What is the proper way of scaling in PDF >> calculation, so that one may obtain the actual structure factor and >> coordination numbers? I used both PDFGetN and PDFGetX to get PDF, and also >> tried to do that by hand. What I found is that however I adjust the >> parameters in both softwares, there is always a scale factor (not equal to >> 1) when one try to refine the obtained G(r) in PDFFit. It seems the scale >> factor is determined by some parameters such as the size of sample and >> vanadium bar, and packing ratios etc, which may not be so accurate when one >> inputs them in PDFGetN. In order to obtain the right coordination numbers, >> the reduced PDF (G(r)=4pi*rho*r[g(r)-1], according to Egami and Billinge's >> definition) must be properly scaled. The scale factor may be found by >> fitting with known model, but may not be so clear for amorphous or unknown >> materials. Is this scale factor arbitrary, or are there some criteria, >> theoretically or empirically? In other words, how can one normalize the >> scattering intensity to get actual structure factor? >> >> Another thing I found is the current version of PDFGetN does not do Lorch >> correction. I am not sure whether there is a new version. >> >> Thanks very much. >> >> Sincerely, >> Ling Yang >> Bldg. 8610, MS 6494 >> Oak Ridge National Laboratory >> Oak Ridge, TN 37830 >> Tel: (865)576 4845 >> Fax: (865)574 1753 > > > > -- > Prof. Simon Billinge > Applied Physics & Applied Mathematics > Columbia University > 500 West 120th Street > Room 200 Mudd, MC 4701 > New York, NY 10027 > Tel: (212)-854-2918 > > Condensed Matter and Materials Science > Brookhaven National Laboratory > P.O. Box 5000 > Upton, NY 11973-5000 > (631)-344-5387 > > email: sb2896 at columbia dot edu > home: http://nirt.pa.msu.edu/ > -- Prof. Simon Billinge Applied Physics & Applied Mathematics Columbia University 500 West 120th Street Room 200 Mudd, MC 4701 New York, NY 10027 Tel: (212)-854-2918 Condensed Matter and Materials Science Brookhaven National Laboratory P.O. Box 5000 Upton, NY 11973-5000 (631)-344-5387 email: sb2896 at columbia dot edu home: http://nirt.pa.msu.edu/
