Re: Powder Diffraction Discussion Group on Facebook
Indeed I find the list one of my best resources and when I have some doubt on a subject, I search the old posts. Kind regards, Roberto Roberto Ribeiro de Avillez Professor Associado Dept de Engenharia Química e de Materiais Pontifícia Universidade Católica do Rio de Janeiro tel. +55 21 3527 1233 On 06/09/2015 12:34 PM, Alan Hewat wrote: the Rietveld mailing list is still where the best knowledgeable is That's encouraging Alan. Thanks. Concerning the number of posts you are right - there are fewer now. I would like to think it's because we have an archive now, and people profit from past answers rather than asking the same questions over again, which used to be common. Or perhaps its because there are now more channels of information. While the number of posts has diminished, the number of members has grown continually. There are now more than 1500, but some well known names only post when they see a particularly interesting question. Whenever there is a good question, we receive good answers. As for insults, I thought Radovan's cleavage between Troglodytes and Tweeters was quite amusing. And every time we have a little controversy, we get new members. One shouldn't assume that because fewer people post, there are fewer people interested. But certainly prepare a graph if you wish. Just don't post it to all 1500+ members :-) Kind regards, Alan. __ * Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE * alan.he...@neutronoptics.com +33.476.98.41.68 http://www.NeutronOptics.com/hewat __ ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Re: on high pressure data indexing and unit cell reduction
Cell conversion may be done with the programs provided by Bilbao Crystallography Server (http://www.cryst.ehu.es/). Consider using the programs: GENPOS and CELLTRAN. On 03/03/2014 05:55 PM, Young, Lindsay wrote: Hello all - I've gotten stuck at a point in my data refinement, I'd appreciate it if someone has any suggestions for me. I have been trying to index high pressure data. It was collected using a diamond anvil cell with a 2d detector. I integrated the data on GSAS II, using the penetration correction. I opened this data on Jade to do peak fitting, and indexed the resulting peak list in Topas. I managed to get a reasonable monoclinic cell - but it is not in standard cell notation - the angle for beta is 142 degrees, and I would like see this cell represented such that is between 90 and 130 degrees. I tried indexing this peak list in Treor and Dicvol, with no results. I then tried putting the unit cell from Topas into hklgen, taking the peaks it generated (which do match those in the pattern), and indexing them with Treor and Dicvol, but neither program turns out any results. I did tweak the standard settings of both programs to try to get results, but this was not successful. The idea is, if we can get the same result in another program as we did in Topas, it could further show that the result is correct. Does anyone know how I can convert this cell? Is there a unit cell reduction program I could use? If you need any additional information please let me know! ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Re: TOPAS full axial model
Hi Lukasz, You are talking about fundamental parameters approach to Rietveld as proposed by Alan Coelho (CHEARY, R. W. e COELHO A., J. Appl. Cryst.,31, 1998, 851-861. ) The sample length is the length of the sample measured in the axial direction (in mm). It is the illuminated area, so it must depend on the source length if you consider the axial divergence. I usually fit all the fundamental parameters using a diffraction from a standard sample and making restrictions for the allowed variations. Then I use the fitted values as the instrument parameters for my samples that use the same geometric arrangement. Best regards, Roberto de Avillez Łukasz Kruszewski escreveu: Hello to all! My name's Lukasz Kruszewski, my interest recently is the mineralogy of burning coal dumps. I'm trying to obtain the unit cell parameters of some members of the alunite group, analysed on Bruker D5005 diffractometer (Co Ka, Bragg-Brentano, RS = 0.6mm wide, FDS = 1 deg.) with use for an article. I pack powdered samples as thin layer on a glass slide with limiters. I would like to kindly ask for help in understanding well the FULL AXIAL MODEL in the INSTRUMENT section of TOPAS program. I know that the SOURCE LENGTH, SAMPLE LENGTH and RS length should be FIXED, but I don't know actually does the SAMPLE LENGHT means. Do I understand well that its the length of the beam focusation area only, or the whole length of the glass slide, or the 'working' distance between source and detector? I would be grateful for any tips (-: With best regards, Lukasz Kruszewski Instutite of Geochemistry, Mineralogy and Petrology Faculty of Geology University of Warsaw __ Informa��o do ESET NOD32 Antivirus, vers�o da vacina 4869 (20100215) __ A mensagem foi verificada pelo ESET NOD32 Antivirus. http://www.eset.com -- Roberto Ribeiro de Avillez Professor Associado Pontifícia Universidade Católica Dept Engenharia de Materiais tel. 55+ 21+ 3527 1250 e-mail: avil...@puc-rio.br __ Informa��o do ESET NOD32 Antivirus, vers�o da vacina 4869 (20100215) __ A mensagem foi verificada pelo ESET NOD32 Antivirus. http://www.eset.com
