Dear All. I fully support the nice idea of Helio for establishing a powder diffraction Database. If we can make it, this will be one of the biggest achievements of these two groups (Rietveld and SDPD). My personal opinion is that such a database will provide excellent opportunities for inter-labs cooperation and will surely improve our skills. The advantages: 1. Large number of powder diffraction patterns with Lab X-ray, neutron and synchrotron will give to the people chance to get familiar with different diffraction spectra, 2. Everyone will have a chance to exercise himself on different samples: well and poorly crystalline, modulated structures, defect structures, standards, pure and mixed materials, 3. Different applications of the Rietveld refinement can be done by number of people: from more routine ones as simple structural refinement, quantification, particles size, site occupancy to some details of the refinement - rigid body adjustment, lattice strain etc., 4. For SDPD purposes the usefulness of such database is even more obvious - one can try to solve the structure by using other approach than the authors + some other varieties in the overall strategy. I think that the goodness of creating and maintaining the Database is obvious for every one. Now, the question is HOW we will do it. My suggestion is that if someone (how about it, Lachlane?) agree to create it we have to set a rules such as: Everyone can submit the file(s) + a written text (free format, in Notepad for easy opening from everyone), in which he have to provide all info about the sample/experiment (if the data are not published yet) + his e-mail address. These of us that will work on his/her sample/pattern will further contact him/her for practical details, instead to bother the rest of the lists. Note that such inter-labs work will give another answer: why quite often the same data refined by different people provide different R-values and even some differences in the refined parameters? This happened this summer, when we refined the same data set using GSAS with Ms. N. from Italy. Anyway, I am really a great supporter of this nice idea and hope that it will be made very soon. However, I do not agree that PDF-3 can do the same job. We are talking about creation of something else - a large varieties of data sets from DIFFERENT samples for improving our capabilities of refining/solution of crystal structures, but not to make any kind of reference database like PDF-3. Regards, Srebri /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ Dr. Sr. Petrov/PXRD Analyses, Dept. of Chemistry, U of T, 80 St.George Str., R.417 Toronto ON M5S 3H6, Canada Tel/Fax: (416)-978-1389. e-mail: [EMAIL PROTECTED]
