Re: RIET: R-factors variation for bond-restrained vs unrestrained refinements
Lachlan, As data may be poor for many reasons, results may be unstable in many ways. In my experience, elimination of the restraints in the final refinement cycles gives always some change in parameters, most time small but sometimes it happens that a homeless atom begins to wander/vanish etc, all without an improvement/change of R. In a few cases, I observed significant changes (both decrease and increase) of R when releasing the restraints. I never published such stuff, probably there's something wrong with the model or the data. Anyway, my use for restraints is mainly as a strategy during refinement, e.g. for group-subgroup transitions, and during the last stage I try to release them all together, except for symmetry restraints which should be kept as should an inversion center, for example. Just for the meaning of the esds! best regards Miguel On 15 Apr 01, at 4:21, Lachlan Cranswick wrote: For people using bond-restraints on medium to large inorganic/zeolite structures to keep things physically reasonable during Rietveld refinement (for data of moderate quality): are there any comments on how R-factors tend to vary if restraints are released - or set to near zero values. Are there negligible drops in R-factors as atoms start wandering away on a holiday in unrestrained refinements vs restrained refinements? (this assumes the model is basically correct) Miguel Gregorkiewitz Dip Scienze Terra, Universit via Laterina 8, I-53100 Siena, Europe fon +39'0577'233810 fax 233938 e-mail [EMAIL PROTECTED]
Re: R: Quartz and others
Dear Maurizio: How do you do? It is interesting to contact people who work in cement industries! Do you determinate clinker phases by XRD? I want to know if you would detail me your method to prepare the samples (standards and unknown ones). I want to determinate CO2 because we add limestone to cements and the quick chemical method lack of precision. Do you determinate quartz in your XRD? Best regards MARCHI Maurizio Para: "'[EMAIL PROTECTED]'" [EMAIL PROTECTED] m.marchi@itccc: gr.net Asunto: R: Quartz and others 12/04/01 03:17 Por favor, responda a rietveld_l i work in a cement company, too for the silica determination by XRD, you can have a look here http://www.osha-slc.gov/SLTC/silicacrystalline/smithdk/index.html for the other questions ... do you want to 'determinate CO2 in cement' by XRD? perhaps you want to determinate free lime in cement ... best regards Maurizio _ Maurizio Iler Marchi Direzione Laboratori - Servizio Analisi e Controlli CTG S.p.A - Italcementi Group Via Camozzi, 124 - 24100 Bergamo - Italy Tel. +39 035 4126 632 Tel.Lab. +39 035 4126 275 Fax. + 39 035 4126 013 E-mail. [EMAIL PROTECTED] _ -Messaggio originale- Da: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Inviato: mercoled 11 aprile 2001 20.27 A: [EMAIL PROTECTED] Oggetto: Quartz and others work in a cement company and I have a Philips XRD 1800. I want to determinate quartz in limestone. I would like to deteminate CO2 in cements and CaCO3 in limestone too. I am new in XRD utilization so I require detailed answers. Is another member who work in a cement industry? Best regards
RE: new GSAS (EXPGUI)
Larry, I knew about this but was hoping that there was a way within Windows to keep the window open. Bob At 06:53 PM 4/14/01 -0700, you wrote: Bob, At 08:06 AM 4/12/01 -0600, you wrote: 2) is it correct that using PC-GSAS the windows automatically close after the program finish? From my point of view it should better to have the possibility to read the refinement results Yes, but I like the windows to stay open too. I havn't found out how tho. Any suggestions are welcome. In my Visual Basic Shell for GSAS, I call the following batch file rather than the executable directly. One only needs to keep the window open for GENLES and a few other programs. @echo off %1 %2 %3 %4 pause I named the script vb-gsas.bat, thus the call to GENLES is vb-gsas.bat genles experiment.exp. The extra arguments take care of any contingencies. Larry -- Larry W. Finger [EMAIL PROTECTED] 1400 Colorado St.Phone: +1 (240) 463-2051 Boulder City, NV 89005 FAX: +1 (209) 844-9855 http://www.lwfinger.net/ Note New URL and E-mail address
problem with gsas for linux
Hi all I've just installed the lates version of GSAS for linux. I followed the instuctions given by Bob and it seemed to install without any difficulties, however every time I want to put in an atom the program crashes and gives me the following message: Give atom editing command (?,$,I,S,X) i n Enter TYPE, X, Y, Z, FRAC or ? for help ni 0 0 0 1 open: No such file or directory apparent state: unit 12 named /home/joost/gsas=/data/atmdata.dat lately writing sequential formatted external IO Abort (core dumped) I put the following in my .bashrc file: alias gsas=/home/joost/gsas/gsas I am not a great expernt on linux and I was wondering if anybody has had a similar problem or knows how to fix this. Thanks Joost Dr. J. van Duijn Department of Physics and Astronomy McMaster University Hamilton, ON Canada L8S 4M1 Do You Yahoo!? Get your free @yahoo.co.uk address at http://mail.yahoo.co.uk or your free @yahoo.ie address at http://mail.yahoo.ie
RE: Size/Strain Round Robin - 1st Report
Dear Leonid and others: Let me comment on two points that were, I think, raised in your message: (i) Whether to keep round-robin results anonymous or not; (ii) How "good" the results actually are. First of all, if anyone chooses to publish his own results on the Web or otherwise, he/she, of course, has every right to do so. However, my firm belief is that I cannot and should not do it for at least two reasons: The first one is obvious; I don't want to put anyone in a position to be (potentially) embarrassed. We had a variety of researchers with different level of experience in line-broadening field (as it should be for a real round robin) and I am particularly thankful to the participants who sent in results, although it was their first time to evaluate size and strain from diffraction data. Second reason: several participants were using commercial software to evaluate size-strain values and/or were from companies that sell XRD equipment or software. I can imagine a situation where a potential customer could take these results (either good or bad, it does not matter) into the consideration when making purchasing decision, which would be unwarranted and a potential liability for the round-robin organizers. Saying all this, I am not arguing that the individual results should be kept secret. We hope to write a full publication where the individual results will be, of course, available (or deposited with IUCr, depending on the editor, I suppose). The report that was posted on the Web is just a condensed (preliminary) version, as I understood from previous postings on this mailing list that some people are eager to see the results as soon as possible. I can also try to "extract" the original results from the e-mails and post them on the Web page, but please, be patient; this takes some time and according to my work plan, I can spend no more than 10 % of my time on the round robin:-) Next issue is about the results. I am asking myself the same thing: Most of the people probably have expected less agreement in size-strain kind of analysis, so "if results are so good, why did you undertake the round robin in the first place?" :-) However, the full publication will hopefully give a more balanced picture of overall results and then everyone will be able to judge whether they are really "impressive" or not. For instance, in the Conclusions it was pointed out that the mean was changed for 73 % if strain was detected. Or even worse, if one considers the scatter of results in domain-size values reported by the participants (among those included in the averages reported on the Web site), say, of volume-weighted domain size: minimum number reported to me was 21.1 and maximum 57.4! Now, I would call that impressive but not exactly with the same connotation:-) However, I think that this kind of scatter was expected. What was a nice result and what, I believe, Leonid is referring to, is a comparison of averages obtained by different methods and especially obtained by different instruments. I believe that the reason for the former is absence of strain and a simple specimen (cubic symmetry, spherical crystallites with isotropic broadening) that was chosen. Some people objected to this, but I think that was the only possibility to give the round robin a fair chance that results won't be wildly different. Besides, more "difficult" sample would disqualify most of the Fourier methods of analysis that could not be applied. The fact that different instruments with very different resolutions gave similar results for size and strain is particularly encouraging. Again, if a specimen with smaller line broadening were selected, probably it would have favored higher-resolution instruments, and the results might have been vastly different. The bottom line, as it looks to me, is: Yes, there was a substantial scatter of results that we expected, but there is a nice agreement between different instruments and methods, which is very encouraging. Especially interesting is a comparison between different instruments because everything else was al ready known from the literature. I hope this justifies why we tried to have measurements collected on different instruments in the round robin, although it might have been a problem for some participants. Best regards, Davor Balzar ** National Institute of Standards and Technology Materials Science and Engineering Laboratory Div. 853, 325 Broadway Boulder, CO 80305-3328 Tel: 303-497-3006 Fax: 303-497-5030 E-mail: [EMAIL PROTECTED] Web: http://www.boulder.nist.gov/div853/balzar European mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/balzar/div853/balzar/ ** -Original Message- From: Leonid Solovyov [mailto:[EMAIL PROTECTED]] Sent: Friday, April 13, 2001 11:14 PM To: [EMAIL PROTECTED] Subject: Re: Size/Strain Round Robin - 1st Report Although my question is addressed to Davor
