Re: Rietveld: U,V,W
Hi, Self Citation: NIST Standard Reference Materials for Characterization of Instrument Performance Industrial Applications of X-ray Diffraction Ed by F. H. Chung D. K. Smith, pp 903-917. A pdf is available; email to request. In this I outline how I use SRM 660 (it was 660 in 2000, then it was 660a until ~July '07, we are working on 660b) for qualifying and characterizing instrument performance with both profile fitting and the Rietveld method, via GSAS. I suggest obtaining a set of TCH parameters with LaB6. The instrument specific ones thereafter remained fixed while the other are used as a floor for refined values. With this approach I was able to obtain stable and meaningful results from laboratory equipment. Regards, Jim At 08:25 PM 11/30/2008, you wrote: To all: What is the correct procedure for refining U,V,W? It is my understanding that those parameters are a function of instrument geometry. Does one use a standard material to determine U,V,W and then fix their values for the instrument you're using?or do the values of U,V,W change depending on the sample being examined? If so, why do the values change? Thanks in advance. Frank May From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Sun 11/30/2008 1:32 PM To: rietveld_l@ill.fr Subject: Re: I am a newcome, how can I begin my rietveld refinement analysis Hi, Li: To me, the most wonderful tool to determine initial peakshape parameters is CMPR. CMPR is especially oriented to GSAS and gives you GU, GV, GW etc. And when you use EXPGUI for GSAS, you can also try Graphs-widplt to see how FWHM develops when parameters are tuned. When you prefer Fullprof, you should take a factor to get U, V, W etc. i am not sure about the facor exactly, maybe GX~100X(X=U, V, W), er..? Anyway, just go ahead and make a try. Faithfully Jun Lu -- Lst. Prof. Lijie Qiao Department of Materials Physics and Chemistry University of Science and Technology Beijing 100083 Beijing P.R. China http://www.instrument.com.cn/ilog/handsomeland/ James P. Cline Ceramics Division National Institute of Standards and Technology 100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ] Gaithersburg, MD 20899-8523USA [EMAIL PROTECTED] (301) 975 5793 FAX (301) 975 5334
Re: % Crystallinity
Hi all, Please prepare for a shameless plug for the newly certified NIST SRM 676a: In order to measure amorphous content (via non-PDF diffraction methods) one needs two things: 1) An unbiased diffraction method for measurement of phase abundance (laughter please) and 2) A standard of known phase purity. A quantitative Rietveld analysis of data from a divergent beam powder diffractometer yields results that are consistently biased by a few percent. The nature of the bias appears dependent on the phases being measured and I don't really know of the origin. But by process of elimination, I think it is due to an over simplistic model for the Lorentz/polarization factor. Therefore, you are better off using nonconventional sources, or accepting that your results may be inaccurate to a few percent. For 10+ years I/we have been pursuing an experimental design to measure absolute phase purity. It has taken several iterations to obtain results I/we cared to talk about. SRM 676 was recertified ~2 years ago for phase purity, however, stocks of it were exhausted (the recertification is retroactive). SRM 676a was released for sale a week or two ago and offers improvements in both the phase purity (99%) and the error bounds on the certified value. See: https://srmors.nist.gov/view_detail.cfm?srm=676A I haven't written the work up yet (I'm working on it); but the experimental design is described in the certificate. Regards, Jim At 06:58 AM 2/27/2008, you wrote: Dear Users, I'm trying to determine the percentage crystallinity in a crystalline/amorphous mixture, could someone point me in a foolproof direction. Thanks, John Free upgrade for your Windows Live Messenger! Click here! James P. Cline Ceramics Division National Institute of Standards and Technology 100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ] Gaithersburg, MD 20899-8523 USA [EMAIL PROTECTED] (301) 975 5793 FAX (301) 975 5334
Opportunity at NIST
Hi all, We have a newly created position for an individual to work with us on the certification of NIST Standard Reference Materials for powder and thin film diffraction and reflectometry methods. The desired background is one with theoretical leanings and competence in programing and data analysis methods. Please don't hesitate to contact Don Windover, 301 975 6102, or myself with any questions. Regards, Jim Official Solicitation: CERAMICS DIVISION MATERIALS SCIENCE AND ENGINEERING LABORATORY (MSEL) NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST) ANALYST, X-RAY METROLOGY AND REFLECTROMETRY STRUCTURE DETERMINATION METHODS GROUP Applications are invited from qualified candidates for a research position involving analytical methods in X-ray reflectometry and reflectivity (XRR), high-resolution X-ray diffraction (HRXRD), and powder diffraction (XRPD) within the Structure Determination Methods Group, Ceramics Division, at NIST in Gaithersburg, Maryland. The position is specific to the X-ray Metrology (XRPD and HRXRD) and XRR projects in the Structure Determination Methods Group, one of four groups in the Ceramics Division. These projects provide the measurement science, Standard Reference Materials (SRMs), and advanced measurement methods needed by U.S. industry to apply XRR, HRXRD, and XRPD techniques across the entire spectrum of materials science and engineering. The Ceramics Division has built SI-traceable X-ray metrology instrumentation featuring advanced X-ray monochromator optics, optical angle encoders, and autocollimation techniques. More information about other activities in the Ceramics Division may be found on our website, http://www.ceramics.nist.gov/http://www.ceramics.nist.gov/. The research position will involve work with experimental data and physical and statistical theories of thin film analysis by XRR and HRXRD, and microstructure (size and strain) analysis by X-ray and neutron powder diffraction. Use of sophisticated statistical methods and theory will be required for parameter estimation and model comparison, e.g., Bayesian and Monte Carlo approaches. Estimating uncertainties in parameters of physical models (particularly uncertainties across various models) from measurements pertaining to SRMs is of paramount interest. The position will require research as part of a project team and participation in efforts with project, Group, and Division leadership to define new measurement directions. Applicants should have experience in implementing data analysis or physical models in mainstream languages for scientific computing (e.g., Python, C, Fortran), preferably with code available for review. It is highly desirable that applicants have a Ph.D. in applied mathematics, computational physics, scientific computing, statistics, physics, materials science, or other related disciplines. Demonstrated completion of projects resulting in publication outputs is required. Experience with specialized environments for instrument control or data analysis (especially Labview, but also Mathematica, Matlab, R) is also valuable. A background in thin films, materials science, or dynamical diffraction or scattering would also be relevant. The position is in the Scientific and Engineering Career Path (ZP) and is initially a two-year appointment, with potential for a permanent appointment. The base salary ranges from $70,000 to $110,000, depending on qualifications and experience. United States citizenship is required. Interested applicants should send a curriculum vita and three references (names and contact information only) via post or e-mail to Dr. Terrell Vanderah, Acting Leader, Structure Determination Methods Group, Ceramics Division, NIST, 100 Bureau Drive, Stop 8520, Gaithersburg, MD 20899, [EMAIL PROTECTED] Applications must be received by April 15, 2008. NIST, a bureau of the U.S. Department of Commerce, is an Equal Opportunity Employer. James P. Cline Ceramics Division National Institute of Standards and Technology 100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ] Gaithersburg, MD 20899-8523USA [EMAIL PROTECTED] (301) 975 5793 FAX (301) 975 5334
Re: Sources of standard reference materials
Hi all, We expect to have SRMs 640d 660b available by no later then November 2008. SRM 676a will available in a ~month. I regret the difficulty that is being caused by this lapse; we are taking measures to prevent them from recurring. Regards, Jim At 09:50 PM 11/15/2007, you wrote: Hi All, Does anyone know an appropriate source of standard reference materials for a line profile standard, like NIST SRM 660a (LaB6) - other than NIST, as they are out of stock and ...is expected to become available by November 2009. Thanks, Ross James P. Cline Ceramics Division National Institute of Standards and Technology 100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ] Gaithersburg, MD 20899-8523USA [EMAIL PROTECTED] (301) 975 5793 FAX (301) 975 5334
Re: SRM676a
Hi All, David, SRM 676a will be available this fall. It is of similar microstructure to SRM 676 and is certified with respect to phase purity. It is, however, at 99%, of much higher purity than SRM 676. Regards, Jim At 02:48 PM 8/21/2007, you wrote: Hi All, I'm looking for a source for NIST 676 alumina powder for use in measuring RIRs for some polymers.The NIST website states that they are out of stock. Does anyone know of other sources for this standard? Thanks, David Lee James P. Cline Ceramics Division National Institute of Standards and Technology 100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ] Gaithersburg, MD 20899-8523USA [EMAIL PROTECTED] (301) 975 5793 FAX (301) 975 5334
Re: RIET: NIST Si 640c cell axis as a function of temperature?
Hi, The temperature issue is one that I have been made to suffer on numerous occasions. My operation was moved to the new NIST Advanced Measurement Laboratory that, among other things, features temperature control, in May of 2004. The parallel beam diffractometer, from which future certification measurements will be obtained, is now located in a 0.01C space. We measure the variation at 0.02C. A divergent beam diffractometer is located in the vestibule for the 0.01C space that is controlled to 0.1C. We haven't measured the variation in this space yet. We are still in the process of commissioning this (largely custom) equipment; however, the parallel beam diffractometer is presently operational in a high-resolution configuration. The first work on powders with the parallel beam diffractometer will include the certification of SRMs 640d, 660b and 1976a in 12-18 months. At 10:52 PM 7/2/2005, you wrote: Is there an official table of NIST 640c Silicon cell axes (with ESD) for when NIST 640c is not exactly measured at 22.5 °C (say anywhere between 5°C to 40°C) Nope. Using the certificate reference via: https://srmors.nist.gov/view_cert.cfm?srm=640C The certified lattice parameter for a temperature of 22.5 °C is 0.54311946 nm ± 0.0092 nm The NIST certificate mentions the thermal expansion coefficient which was applied to the measured peaks. The temperature variation during the data collection for SRMs 640c and 660a was +/- 1.5C. The data, therefore, embody both a simple thermal expansion effect from the specimen itself, and a second, more complex one from the equipment. The separation of the two is non-trivial. We applied a simple thermal expansion correction to the data of the silicon, and, to a first approximation, did not see a instrument contribution. For those who like their XRD calibrations and/or wavelengths backed up all the way with a bit of NIST Onion Paper, it would be nice to have such a table (or the range in which the stated thermal expansion coefficient in the certificate (and certificate ESD) is valid). (Some labs have different air-conditioning temperatures / or lack of room temperature control). Measurements at specific temperatures would require the construction of a furnace assembly that would have to embody some non-trivial engineering: There could be no temperature differential between it and the goniometer assembly; thermal transfer between it and the atmosphere would have to be minimal ( 10 watts ); volumetric, homogeneous temperature control to ~.05C; and a sample spinner. I'll think about it in earnest after the certification of the next series of line position SRMs (and perhaps a low angle line position SRM). Best, Jim James P. Cline Ceramics Division National Institute of Standards and Technology 100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ] Gaithersburg, MD 20899-8523USA [EMAIL PROTECTED] (301) 975 5793 FAX (301) 975 5334
Re: fundamental parameters approach X'celerator
Arie, Bob Cheary developed the required description/equations for the use of a psd. But I don't know that they have been implemented in any of the available FPA codes, except perhaps Topas in launch mode. Alan??? Are you listening? Regards, Jim At 06:48 AM 5/2/2005, you wrote: Dear colleagues, Is there anybody who has experience with describing peak shapes using the fundamental parameters approach for a typical X'pert-pro diffractometer setup with an X'celerator detector (fixed incident slits, 0.02 rad sollers, no monochromator)? Thanks in advance, Arie *** A. van der Lee Institut Européen des Membranes (UMR 5635) Université de Montpellier II - cc 047 Place E. Bataillon 34095 Montpellier Cedex 5 FRANCE visiting address: 300 Av. Prof. E. Jeanbrau tél.: 00-33-(0)4.67.14.91.35 FAX.: 00-33-(0)4.67.14.91.19 *** James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: fundamental parameters approach X'celerator
Indeed... A situation not without some complications. Jim At 08:00 AM 5/2/2005, you wrote: Alan??? Are you listening? Bruker providing help to analyze Panalytical data ?-). Armel James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: fundamental parameters approach X'celerator
Laurel, At 09:13 AM 5/2/2005, you wrote: Hi, Alan Coelho helped us get our instrument parameter file set up for Topas Academic. We use an X'celerator detector with cobalt radiation (no monochromator) for most of our work. Here is an example file: xdd test.dat CoKa7_Holzer(0.001) Radius(240) LP_Factor(17) axial_conv filament_length 12 sample_length 15 receiving_slit_length 12 primary_soller_angle @ 5 This is curious: it is the basic criteria one would use for the full axial model of Topas. It has nothing to do with a PSD. Jim Hope this helps. Laurel Basciano At 06:48 AM 5/2/2005, you wrote: Dear colleagues, Is there anybody who has experience with describing peak shapes using the fundamental parameters approach for a typical X'pert-pro diffractometer setup with an X'celerator detector (fixed incident slits, 0.02 rad sollers, no monochromator)? Thanks in advance, Arie *** A. van der Lee Institut Européen des Membranes (UMR 5635) Université de Montpellier II - cc 047 Place E. Bataillon 34095 Montpellier Cedex 5 FRANCE visiting address: 300 Av. Prof. E. Jeanbrau tél.: 00-33-(0)4.67.14.91.35 FAX.: 00-33-(0)4.67.14.91.19 *** -- Laurel Basciano Department of Geological Sciences and Geological Engineering Queen's University [EMAIL PROTECTED] (613)484-1911 James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: fundamental parameters approach X'celerator
Arie, Yes; Bruker has an interest in this matter. Jim At 09:37 AM 5/2/2005, you wrote: Bruker's Vantex detector is rather similar to PanAnalytical's X'celerator detector from a fundamental parameters point of view, not? Maybe I should have formulated my question differently Is there anybody who knows how to model peak shapes using the fundamental parameters approach for diffractometer setups with the newly developped PSD's such as the Vantex and X'celerator? Nobody will be vexed in this way, I hope at least Arie ps: and thanks, Laurel, for the suggestion, I'll try that. Indeed... A situation not without some complications. Jim At 08:00 AM 5/2/2005, you wrote: Alan??? Are you listening? Bruker providing help to analyze Panalytical data ?-). Armel *** A. van der Lee Institut Européen des Membranes (UMR 5635) Université de Montpellier II - cc 047 Place E. Bataillon 34095 Montpellier Cedex 5 FRANCE visiting address: 300 Av. Prof. E. Jeanbrau tél.: 00-33-(0)4.67.14.91.35 FAX.: 00-33-(0)4.67.14.91.19 *** James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: request
Venkat, Care to count up the number of requests you have made of the members of this Rietveld Listserv? Is this an online library/database? Jim At 07:10 PM 4/20/2005 +0630, you wrote: Thanks very much for bothering +++ M Venkata Kamalakar Junior Research Fellow, S.N.Bose.National Centre for Basic Sciences, Block-JD, Sector-3, Salt Lake, Kolkata, Pin: 700 098. Phone no: 033 23355705/6/7/8 Extn: 404, 104, 301. +++ -- Original Message --- From: Jim Cline [EMAIL PROTECTED] To: rietveld_l@ill.fr Sent: Wed, 20 Apr 2005 07:31:57 -0400 Venkat, What journals does your institute subscribe to? Jim At 05:25 PM 4/20/2005 +0630, you wrote: Dear all, Can anyone please send me the following paper. Ferroelectrics Publisher: Taylor Francis Volume: Volume 306 / 2004 Pages: 95 - 109 URL: Linking Options DOI: 10.1080/00150190490458437 GlassCeramicMetal Nanocomposites Containing a Ferroelectric Phase A. DAN A1, T. K. KUNDU A2, B. SATPATI A3, P. V. SATYAM A3, D. CHAKRAVORTY A4 It very essential and our institute doesn't subscribe it. Thankyou venkat +++ M Venkata Kamalakar Junior Research Fellow, S.N.Bose.National Centre for Basic Sciences, Block-JD, Sector-3, Salt Lake, Kolkata, Pin: 700 098. Phone no: 033 23355705/6/7/8 Extn: 404, 104, 301. +++ James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA --- End of Original Message --- James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: Size Strain in GSAS
Hi, In response to some of this post: There was a move by a bunch of us in the ICDD to hold a profile fitting round robin ( which I think would by quite useful ). But it died when we realized the prodigious level of resources that would be required to make sense of the rather large matrix of data that would arrive. But with regards to a round robin on this question: seems to me some qualified individual could simply do the work and publish a nice paper on it. Regards, Jim At 12:30 PM 4/15/2005 +0200, you wrote: urn:schemas-microsoft-com:office:office Nicolae, Nick, Bob, Leonid, I have looked at many patterns (recorded by others) and a few cases have shown profiles that are sharper that a Lorentzian; whereby sharper means that the integral breadth is smaller than that for a unit area lorentzian. To put a figure on it would be difficult but at a guess I would say 3% of patterns fall into this category in a noticeable manner. I have no doubt that the work of Nick Armstrong and co. is mathematically sound but a simulated data round robin as suggested by Leonid Solovyov may be useful and I am not generally a fan of round robins but this s different as the data is simulated. A pure peak fitting approach shows that two pV s (or two Voigts) when added with different FWHMs and integrated intensities but similar peak positions and eta values can almost exactly fit Pearsons II functions that are sharper that Lorentzians. This is not surprising as both profiles comprise 6 parameters. Thus from my observations two pVs added together can fit a bimodal distributions quite easily. In fact my guess is that two pVs can fit a large range of crystallite size distributions. Thus distinguishing whether a distribution is not monomodal is of course possible especially if the two pV approach is taken. Attempting to determine more than that however takes some convincing as two pVs seem to fit almost anything that I have seen that is symmetric. Thus introducing more pVs seems unnecessary. Thus yes GSAS can determine if a distribution is not monmodal if you were to fit two identical phases to the pattern except for the TCH parameters. If the Rwp drops by .1% then I wont be convinced. Forgive me Nick but I have not yet read all of your work and I am certain that it is sound. Outside of nano particles (and maybe even inside) my reservation are that we may well be analyzing noise and second order sample and instrumental effects. Thus to show up my naive ness can you categorically say that there are real world distributions that two pseudo Voigts cannot fit because I have not come across such a pattern. Once you have done that then it would be time to concentrate on strain, micro strain, surface roughness and then disloactions all the best alan -Original Message- From: Nicolae Popa [mailto:[EMAIL PROTECTED]] Sent: Friday, April 15, 2005 9:30 AM To: rietveld_l@ill.fr Subject: Re: Size Strain in GSAS Dear Bob, Perhaps I was not enough clear. Let me be more explicit. It's about one sample of CeO2 (not that from round-robin) that we fitted in 4 ways. (i) by GSAS with TCH-pV (ii) by another pV resulted from gamma distribution of size (iii) by Lorentz - (the limit of any regular pV - eta=1) All these 3 variants given bad fits. For example (ii): Rw=0.144, similarly the rest. (In principle if one pV works (TCH for example) any other kind of pV must work.) (iv) by the profile resulted from lognormal distribution of size; this time the fit was reasonably good: Rw=0.047. It resulted c=2.8, that means a super Lorentzian profile (I remember that the Lorentzian limit for lognormal is c~0.4 - JAC (2002) 35, 338). Attention, this super Lorentzian profile is not constructed as a pV with eta1. Sure, such samples are rare, or, perhaps, not so rare. A Jap. group (Ida,, Toraya, JAC (2003) 36, 1107) reported super Lorentzian on a sample of SiC. They found c=1.37 Best wishes, Nic Popa Nic, This is true for the internal math but the TCH function was assembled to reproduce the true Voigt over the entire range of differing Lorentz and Gauss FWHM values so it works as if the two FWHM components are independent. As for your question, I'm not aware that anyone has actually tried to do the fit both ways on a super Lorentzian (eta1 for old psVoigt) sample to see if a) the fit is the same and b) the eta1 was an artifact. Any takers to settle this? Bob R.B. Von Dreele IPNS Division Argonne National Laboratory Argonne, IL 60439-4814 -Original Message- From: Nicolae Popa [mailto:[EMAIL PROTECTED]] Sent: Thursday, April 14, 2005 9:11 AM To: rietveld_l@ill.fr Subject: Re: Size Strain in GSAS Dear Bob, If I understand well, you say that eta1 (super Lorenzian) appeared only because eta was free parameter, but if TCH is used super Loreanzians do not occur? Nevertheless, for that curious sample of cerium oxide we tried GSAS (with TCH) and the fit was very bad. Best wishes, Nicolae PS. By the way, TCH also forces
RE: Size Strain [ In GSAS ??? ]
Hi all, Well, I thought I'd weigh in on this with a discussion of an aforementioned SRM project: We are in the final stages of preparing an SRM for determination of crystallite size from line profile analysis. Through the course of his PhD work and NIST postdoctoral position, Nick Armstrong has developed a MaxEnt / Bayesian method specifically for the certification. The method can quantify, from the quality of the raw data, the probably that a proposed model for the crystallite size distribution is the true one. Thus, the certified values of the standard will include a valid measure of their uncertainty that, in our humble opinion, would not be obtainable with alternative methods. Details, and results of the method as applied to the RR CeO2, have been published. We are working at the production of ~kg quantities of strain free CeO2 and ZnO for use as the SRM feedstock; no small challenge. We expect two outcomes: 1) The community will have a standard by which results from mortal methods may be readily tested and compared. 2) A high-intensity squabble will ensue as to whether or not we got the right answer. With regards to the latter issue: Nick and I have been approached about another round robin. Forgive me, but: round robins don't have anything to do with accuracy. They test for uniformity of measurements in the field, the major premise being that, as a result of mature methodology, a narrow distribution is expected. Note the highly successful, Rietveld, QPA, and instrument sensitivity round robins. There is, however, no mature methodology here. Indeed, only a small number of operations worldwide can perform a credible microstructure analysis, and their methods certainly differ. It is our intention to make the data collected for the certification available to the community. But with regards to model testing for the more advanced, physical model, methods (with the use of simulated, bi-model data for instance), I would suggest that more of a collaborative effort be organized. Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: Size Strain In GSAS
Hi, Nick Armstrong has advised me he will in non-email-land for a week or so. I'm sure he'll resume this discussion when he returns... Jim At 03:45 PM 3/28/2005 +0400, you wrote: Hi, So, to resume your statements, by using Bayesian/Max.Entr. we can distinguish between two distributions that can not be distinguished by maximum likelihood (least square)? Hard to swallow, once the restored peak profiles are the same inside the noise. What other information than the peak profile, instrumental profile and statistical noise we have that Bayes/Max.ent. can use and the least square cannot? prior distributions to be uniform - if I understand correctly you refer to the distributions of D0 and sigma of the lognormal (gamma) distribution from which the least square chooses the solution, not to the distribution itself (logn, gamm). Then, how is this prior distribution for Baye/Max.ent.? Best, Nick Popa Hi Sorry for the delay. The Bayesian results showed that the lognormal was more probable. Yes, the problem is ill-condition which why you need to use the Bayesian/Maximum entropy method. This method takes into account the ill-conditioning of the problem. The idea being it determines the most probable solutions from the set of solutions. This solution can be shown to be the most consistent solution or the solution with the least assumptions given the experimental data, noise, instrument effects etc (see Skilling Bryan 1983; Skilling 1990; Sivia 1996). This is the role of entropy function. There are many mathemaitcal proofs for this (see Jaynes' recent book). The Bayesian analysis maps out the solution/model spaces. Also the least squares solution is simple a special case of a class of deconvolution problems. This s well established result. It is not the least ill-posed, since it assumes the prior distributions to be uniform (in a Bayesian case. See Sivia and reference therein). In fact it's likely to be the worst solution since it assumes a most ignorant state knowledge (ie. uniform proir) and doesn't always take into consideration the surrounding information. Moreover, it doesn't account for the underlying physics/mathematics, that the probability distributions/line profiles are positive additive distributions (Skilling 1990; Sivia 1996). Best wishes, Nick Dr Nicholas Armstrong snip James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: Size Strain In GSAS
Hi, I wrote an article [ that appeared in Dean Smith's book ] some time back that describes how to use SRM 660a, LaB6, and the TCH function of GSAS for characterization of the IPF, and then refine the only the microstructure specific terms for an estimation of the size and strain in subsequent analyses. The approach has its limitations for sure, but it is accessible with a small effort. Regards, Jim At 02:10 PM 3/25/2005 +0100, you wrote: Dear Andreas, I didn't said it cannot be done. Only that was not made for and so it is not easy as using other tools. In principle every diffraction fitting program can be used for size-strain. Few questions: have you ever tried to do such analysis with GSAS the right way using the instrumental profile correction? Did you use only GSAS for that or you had to use other external tools/computations? (this to get a feeling about your statement: Thus, on this level of line broadening analysis, everything necessary is contained in GSAS; may be level should be clarified). I would like to know what there is inside GSAS for crystallite size and microstrain analysis in particular. Best regards, Luca Lutterotti On Mar 25, 2005, at 12:55, Andreas Leineweber wrote: Dear all, I think the statement that one cannot do line-profile analysis using GSAS is too strong. In principle it is possible to do some size strain analysis using GSAS, if the instrumental profile is e.g. sufficiently described previously by the Thompson-Cox-Hastings (TCH) profile function (includes measuring corresponding data on a suitable standard). I think, even involvement of the Finger asymmetry correction does not introduce systematic errors. Then the increase in the tantheta and 1/costheta related Gaussian and Lorentzian line width components of the TCH description upon Rietveld refinement on the basis of diffraction data exhibiting physical line broadening can in principle be associated with microstrain- and size-related quantities. This can also be extended by involving anisotropic size and microstrain models. Thus, on this level of line broadening analysis, everything neccessary is contained in GSAS. Of course, something like microstrain and size distributions cannot be obtained using GSAS. Of course there are problems: 0. Microstrain broadening must be proportional to tan(theta). This is not neccessarily the case. There mustn't be further line broadening contributions like stacking faults, complicating the situation. 1. If both size and strain contributions are present, one most be aware of the correlation between the tantheta and 1/costheta dependent compontents. 2. One has to be aware to which average values of the size and microstrain distributions the increases of the line width parameters can be associated with. This requires for GSAS a close analysis of the GSAS manual (how are the line-width paramerters defined!) and line broadening literature, how such pseudo-Voigt line width parameters can be related with averages microstructure parameters. Thus it is not made easy for the user to extract something like that from the line width parameters. But perhaps it is better that way, because consequently the user is forced to to deal himself with the required theory, rather than just refining a parameter called size and one called microstrain, believing in the results and publish the values Definitely there are much better procedures to analyse size and microstrain than by GSAS. So, going to the problem of Apu: If the instrumental profile is well described before using TCH, refinement of (only) LX (and perhaps P) gives you quantities whiuch you should be able to relate to size related quantities upon reading the GSAS manual and some line broadening literature. Best regards Andreas Leineweber Dear Prof. Lutterotti, I was also aware of the fact that GSAS is not made for Size Strain analysis. I got interested to use the Size strain refinement feature of GSAS only after going through the article : Size-strain line broadening analysis of the ceria round-robin sample by Prof. D. Balzar et. al. Journal of Applied Crys. 37(2004)911-924. In that round robin results they have reported the size strain obtained from GSAS. I my case also when I am trying with GSAS, the diffraction pattern is fitting well except the peak braodening. I think this brodening is due to small domain size effect. I that case how will I obatin a good fit with GSAS. Thanking you. Best Regards, Apu /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ Apu Sarkar Research Fellow Variable Energy Cyclotron Centre Kolkata 700 064 phone: 91-33-2337-1230 (extn. 3190) Fax: 91-33-2334-6871 INDIA /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ - Original Message - From: Luca Lutterotti [EMAIL PROTECTED] Date: Friday, March 25, 2005 3:31 pm Dear Apu, I know I will start up a good debate here, but size-strain analysis with GSAS is a
Re: request
Hi all, Its getting to the point that 75% of the posts on this list are requests for structures and articles??? Inappropriate. Jim At 11:33 AM 3/23/2005 +0530, you wrote: Dear all, Can anyone please send me the following article. snip James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
RE: Enquiry of XRD standard materials (fwd)
Hi, At 02:09 PM 12/7/2004 +, you wrote: Dear Stephen, I have prepared XPD-standard Y2O3 by firing Y2O3 (99.999) from Aldrich at 1200 ºC for 72 hs. (as done in 41-1105 PDF card). I would also like to ask the other list members if anyone has calibrated the size-strain broadening of Y2O3 against LaB6, because I have no access to LaB6 and I've heard that yttria gives broader lines. Thanks Leopoldo From Y2O3 annealed at around 1200 degC, and using fundamental parameters peak fitting in XFIT (BGMN and Topas are currently maintained programs), I get around 3300 Angstrom for crystallite size - and near zero strain (using the size/strain modelling defaults in XFIT). Though don't have a comparison with LaB6. What is the certificate crystallite size and strain value for NIST LaB6 - via Google, the NIST website seems to be giving a problem finding this out? http://ois.nist.gov/srmcatalog/certificates/view_cert2pdf.cfm?certificate=660a Error Occurred While Processing Request Error Diagnostic Information An error has occurred. HTTP/1.0 404 Object Not Found Lachlan ??? Works for me: https://srmors.nist.gov/view_cert.cfm?srm=660A We estimate the crystallite size of SRM 660a to be 2 microns, and could not find any strain broadening, from an FPA (Topas) analysis of conventional, lab XRD data. We have compared SRM 660a to the super NAC at ESRF/BM16; but results are qualitative. We would, of course, like to quantify the broadening of SRM 660a, but the project is a bit of a can-of-worms that will have to wait, perhaps until the certification of SRM 660b in ~2 years. Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: back loading
Hi, At 08:38 AM 9/10/2004 +0200, you wrote: Hello Andreas, When I met Jim Cline at the Denver Conference he spoke about a fluid to drop into a (possibly backloaded) powder sample in order to make it solid. I will not put Jim's e-mail address on the Rietveld list but am quite sure he is subscribed - Jim, could you advise? Me??? But I was having so much fun in lurk mode... There exists a single component, moderate viscosity, low wetting angle epoxy designed and sold for quick fixes to leaky vacuum equipment. The stuff is supposed to seek into and fill cracks, then harden into a semi-flexible seal. I have found that a very small quantity of it can be used to stabilize compacts of powders as, due to the low wetting angle, it will fully infiltrate such a compact before hardening. I have not found that it has any impact on the measured background. However, in order to employ it for this, back loading, application, one would have to come up with a smooth surface to which the epoxy would not adhere. I would certainly try Teflon, but some experiments are in order. Best regards, Jim snip James P. Cline[EMAIL PROTECTED] Ceramics DivisionVoice (301) 975 5793 National Institute of Standards and TechnologyFAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523 USA
Re: Quantitive analysis
Hi all, This is to say that I'm am nearly finished with the re-certification of SRM 676 for amorphous content. The revised certificate, offering a discussion as to the certification method, will be on the NIST website shortly, after the review process is completed. The certified phase purity of SRM 676 (retroactive to units in the field) is 91.75% +/- 1.5%. Regards, Jim At 01:44 PM 5/6/2004 -0400, you wrote: Robert As previously mentioned many Rietveld programs will do what you want if you're willing to do the amorphous content calculations by hand afterwards. Some commercial software has it built in. I've done work in this area, and there are some pitfalls of which you must be aware, or your results may be VERY unreliable. 1. microabsorption. If your phases are similar in composition and your 'spike' phase has a similar absorption then this might not be a problem. However, there are instances in which extreme microabsorption can make a accurate determination practically impossible (other than possibly changing your tube to a more friendly wavelength). There is the Brindley correction that can sort of correct moderate microabsorption, but you need to know your particle size, and ideally it needs to have a narrow distribution. Reducing the particle size of your sample to sub-micron levels helps significantly. 2. spike phase. Many so-called crystalline phases aren't as fully crystalline as you might think. The SRM676 alumina had it's amorphous content measured a while back using neutrons and came out as 1.77 +- 0.68%. It doesn't sound alot but can make a big difference to your final results. Many 'crystalline' phases can be significantly higher. Microabsorption can be an issue with the spike so choose your spike carefully, and ideally standardise it using SRM676. Remember to include the error in the SRM676 amorphous content if quoting absolute amorphous contents rather than relative amounts. 3. particle statistics. This is equally as important when looking at purely crystalline materials, but errors due to poor particle statistics can really mess up amorphous content work. Ideally, micronise your sample before running it, but if they're nanomaterials then it might not be an issue. 4. surface roughness. I noticed that you probably work with nanomaterials. They tend to be fluffy, and such samples (at least on our instrument) show noticeable surface roughness effects on low angle reflections. If this is the case for your samples then you will either have to correct it or densify your sample somehow (or both). Some of this stuff was covered in the results of the quantitative analysis round robin a while back: Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 1a to 1h I. C. Madsen, N. V. Y. Scarlett, L. M. D. Cranswick and T. Lwin, J. Appl. Cryst. (2001). 34, 409-426 Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticals N. V. Y. Scarlett, I. C. Madsen, L. M. D. Cranswick, T. Lwin, E. Groleau, G. Stephenson, M. Aylmore and N. Agron-Olshina J. Appl. Cryst. (2002). 35, 383-400 It would be useful to cross-check your technique on a couple of dummy samples if at all possible to make sure you're not being mislead. Have fun!! Pam Dr Pamela Whitfield CChem MRSC Energy Materials Group Institute for Chemical Process and Environmental Technology Building M12 National Research Council Canada 1200 Montreal Road Ottawa ON K1A 0R6 CANADA Tel: (613) 998 8462 Fax: (613) 991 2384 Email: mailto:[EMAIL PROTECTED] ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca -Original Message- From: Robert Mauricot [mailto:[EMAIL PROTECTED] Sent: May 6, 2004 10:57 AM To: [EMAIL PROTECTED] Dear all, I have a powder diffraction of an amorphous multiphase material. I want to do a quantitative analysis of the amorphous phase. Can anyone tell me what software does it. Sincery R.mauricot Cemes-CNRS Toulouse 31077 France Laboratoire NaNomat James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8520 Gaithersburg, MD 20899-8523USA
Re: Quantitive analysis
Hi, At 03:48 PM 5/6/2004 -0400, you wrote: Jim Excellent news! This amorphous standard issue has been driving me nuts. When you say phase purity do you mean purity in terms of crystalline phase content? Yes. Jim Pam Dr Pamela Whitfield CChem MRSC Energy Materials Group Institute for Chemical Process and Environmental Technology Building M12 National Research Council Canada 1200 Montreal Road Ottawa ON K1A 0R6 CANADA Tel: (613) 998 8462 Fax: (613) 991 2384 Email: mailto:[EMAIL PROTECTED] ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca -Original Message- From: Jim Cline [mailto:[EMAIL PROTECTED] Sent: May 6, 2004 3:43 PM To: [EMAIL PROTECTED] Hi all, This is to say that I'm am nearly finished with the re-certification of SRM 676 for amorphous content. The revised certificate, offering a discussion as to the certification method, will be on the NIST website shortly, after the review process is completed. The certified phase purity of SRM 676 (retroactive to units in the field) is 91.75% +/- 1.5%. Regards, Jim At 01:44 PM 5/6/2004 -0400, you wrote: Robert As previously mentioned many Rietveld programs will do what you want if you're willing to do the amorphous content calculations by hand afterwards. Some commercial software has it built in. I've done work in this area, and there are some pitfalls of which you must be aware, or your results may be VERY unreliable. 1. microabsorption. If your phases are similar in composition and your 'spike' phase has a similar absorption then this might not be a problem. However, there are instances in which extreme microabsorption can make a accurate determination practically impossible (other than possibly changing your tube to a more friendly wavelength). There is the Brindley correction that can sort of correct moderate microabsorption, but you need to know your particle size, and ideally it needs to have a narrow distribution. Reducing the particle size of your sample to sub-micron levels helps significantly. 2. spike phase. Many so-called crystalline phases aren't as fully crystalline as you might think. The SRM676 alumina had it's amorphous content measured a while back using neutrons and came out as 1.77 +- 0.68%. It doesn't sound alot but can make a big difference to your final results. Many 'crystalline' phases can be significantly higher. Microabsorption can be an issue with the spike so choose your spike carefully, and ideally standardise it using SRM676. Remember to include the error in the SRM676 amorphous content if quoting absolute amorphous contents rather than relative amounts. 3. particle statistics. This is equally as important when looking at purely crystalline materials, but errors due to poor particle statistics can really mess up amorphous content work. Ideally, micronise your sample before running it, but if they're nanomaterials then it might not be an issue. 4. surface roughness. I noticed that you probably work with nanomaterials. They tend to be fluffy, and such samples (at least on our instrument) show noticeable surface roughness effects on low angle reflections. If this is the case for your samples then you will either have to correct it or densify your sample somehow (or both). Some of this stuff was covered in the results of the quantitative analysis round robin a while back: Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 1a to 1h I. C. Madsen, N. V. Y. Scarlett, L. M. D. Cranswick and T. Lwin, J. Appl. Cryst. (2001). 34, 409-426 Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticals N. V. Y. Scarlett, I. C. Madsen, L. M. D. Cranswick, T. Lwin, E. Groleau, G. Stephenson, M. Aylmore and N. Agron-Olshina J. Appl. Cryst. (2002). 35, 383-400 It would be useful to cross-check your technique on a couple of dummy samples if at all possible to make sure you're not being mislead. Have fun!! Pam Dr Pamela Whitfield CChem MRSC Energy Materials Group Institute for Chemical Process and Environmental Technology Building M12 National Research Council Canada 1200 Montreal Road Ottawa ON K1A 0R6 CANADA Tel: (613) 998 8462 Fax: (613) 991 2384 Email: mailto:[EMAIL PROTECTED] ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca -Original Message- From: Robert Mauricot [mailto:[EMAIL PROTECTED] Sent: May 6, 2004 10:57 AM To: [EMAIL PROTECTED] Dear all, I have a powder diffraction of an amorphous multiphase material. I want to do a quantitative analysis of the amorphous phase. Can anyone tell me what software does it. Sincery R.mauricot Cemes-CNRS Toulouse 31077 France Laboratoire NaNomat James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards
Re: LaAlO3 structure
Joerg, At 07:07 AM 3/7/01 +, you wrote: snip We have done some investigations on the old line standard LaB6 SRM660, it contains some minor phases (sum 5%), one was LaAlO3. The new standard SRM660a is clean and has some other advantages, too. Now, we favour SRM660a over Y2O3. This is a pleasant report to hear! Will I see you at Accuracy in Powder Diffraction III? Best regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523USA
Re: SRMs 640c 660a
At 04:42 PM 9/29/00 +0200, you wrote: Jim wrote: The hydrostatic stress level is inversely proportional to the radius of curvature of the particles. Therefore, the Exactly, how did you determine the trend? Have you measured the cell parameters for different granulometries? This view of the matter came from consideration of surface tension effects on droplets. The hydrostatic compressive stress on a droplet due to surface tension is inversely proportional it's size. There is circumstantial evidence in the literature on the observance of a reduction in lattice parameter with a reduction in crystallite size. But I don't know that anyone has actually set out to due a systematics study of this effect. It does, however, follow that this purely geometric effect will operate in reverse, i.e., surface compression for surface tension and hydrostatic tension for hydrostatic compression. Last curiosity. The old SRM 640b was having a certified cell parameter slightly smaller than the crystal used for 640c. Do you think that in this case it was not measured correctly the "absolute value" or it "was" different? Interesting question: The certification methods for the two SRMs were completely different (this is why SRM 640c has been so long in arrival). Therefore, it is difficult to say why the two certified cell parameters are different. I may look into this in the future. I am building a new diffractometer for certification of SRMs and this is a problem to which it will be well suited. Sorry for the question, but I personally and philosophically don't think we can measure absolute values.. I disagree; and I enjoy my job too! Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523USA
SRMs 640c 660a
Hi all, This is to indicate that NIST SRMs 640c, silicon powder, and 660a, lanthanum hexaboride powder, are available from the NIST SRM Program sales office. These SRMs are certified with respect to lattice parameter at the part-per-million level. Considerable effort has been expended to tailor the microstructure of these SRMs to exhibit a minimal level of particle size and micro-strain induced profile broadening. Please see: http://ois.nist.gov/srmcatalog/certificates/view_cert2gif.cfm?certificate=640c and http://ois.nist.gov/srmcatalog/certificates/view_cert2gif.cfm?certificate=660a for views of the certificates which offer a description of the material and the certification method. Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523USA ** NIST Standard Reference Materials Program Phone: 301 975 6776 FAX:301 948 3730 email: [EMAIL PROTECTED] Home Page: http://www.nist.gov/srm Please see home page for copies of NIST SRM certificates. **
Re: mirror vs. Ge monochromator.
Hi, At 08:46 AM 7/7/00 +0100, Joe Hriljac wrote: When we faced the same decision (well, only one machine, UK oil money does snip I agree with Joe: I have a D500 with a Ge monochromator and a PSD. I don't like the metal wire PSD as much as the quartz wire one as it imparts noise to the data in excess of expected counting statistics but the machine offers high resolution and stability with no alpha 2 or other junk. If the machine is properly aligned and samples are properly mounted than one can count on predicable delta d alignment curves. I believe the jury is still out on high resolution / high accuracy data from mirror optics. They do offer "freedom" from sample displacement errors; but there are additional complications. I'll be speaking on this at Denver. At 10:27 AM 7/7/00 +0200, Stan Gierlotka wrote: 1) Ge monochromator + PSD - no Ka2, extremely good counting statistics, but somewhat broadened and uncertain peak shapes 2) Geobel mirror + LiF analyzer crystal - nice peak shapes down to very low angles, very reliable peak positions but long counting times. I disagree: If you've got "uncertain" peak shapes from your Ge monochromator than you've got uncertainty somewhere in your mounting/alignment of it. The Ge crystal can resolve the alpha 1 from the alpha 2 without distortion; however, you do need a slit at the focal point (line) to block scatter (the instructions supplied with the Siemens D500 setup don't mention this but the system is designed to allow it). The mirror with an LiF analyzer is something I'd like to try out. Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523USA
RE: Si lattice parameter
Hi, At 05:26 PM 4/17/00 +0200, you wrote: Dear All, I would like to add the following question concerning the standard Si powder. Is there someone who has information on the grain size of the 640b Si material ? snip The mean particle size of SRM 640b, via laser scattering, is 7.3 microns. However, the distribution is fairly broad with the fines tail extending well into the submicron region. Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523USA
Re: Kalpha2
Hi, At 07:31 PM 4/1/00 +0200, you wrote: I'm looking forward for many discussions! Yep! I have some naive questions : I would like to hear exactly what is on my powder pattern: - Kalpha3 - tube tails or both ?? The paper by G. H"olzer et al. (Phys. Rev. A 56 (1997) pp. 4554 ff.) is (at present) the definitive paper on emission spectra, and they do not discuss the presence of the "Kalphs3". However, I believe it is referenced elsewhere (I'll look into it) and, as I have said, it can be readily seen in the experiment I described previously (anyone who wants a .pdf plot can email me). I would like to see (or do) the single crystal experiment in order to definitively characterize the "tube tails". I suspect that the answer to the Armel's question is both. Do these effects would occur at the same angular value ? Nope; the "Kalpha3" is observed on the low angle side of the profile while the "tube tails" are observed on both sides. Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523USA
Re: Kalpha2
Hi, Verification of tube tails with a single crystal experiment has been obtained: I called Keith Bowen of Bede on this thread as I thought he would be interested in this matter and I know he is knowledgeable on electron beam focusing. [See the Bede web site and look for Microsource.] He pointed out that the distribution of Xray sources across the anode could be imaged with a Bartels monochromator and the scanning could be done with a suitably small detector slit. In an hour the experiment was complete. From Keith: The detector slit was 50 mm, at 750 mm from the source, and could be scanned across the beam. The monochromator has an output divergence of 5 arc seconds (2.5 x 10-5 radians) so will give a blurring of about another 20 mm, providing a spatial resolution overall of about 70 mm. The tube was a Siemens ceramic K FN Cu 2K, run at full power, with nominal focus 10 x 1 mm. It was run in vertical line mode with a takeoff angle of 6. The maximum count was 17,500 cps and lobes were observed at about 15 cps [as shown in figures he sent me]. The lobes were not symmetric [they span a detector Z range of -0.4 to +0.6mm with the central focal line from -0.15 to +0.15mm]. These lobes are lower than reported by Joerg Bergmann in www.bgmn.de/tubetails.html, but also the tube is a more modern design. 1/sin(6 [deg take off]) X 0.5 mm [detector Z] = 4.78 mm: The origin of the X-rays of one lobe is ~5 mm from the focal line. While the count rate is low (for the narrow spectral window of the monochromator), this is not such good focusing. Somebody should invent a better mousetrap! Regards, Jim James P. Cline[EMAIL PROTECTED] Ceramics DivisionVoice (301) 975 5793 National Institute of Standards and TechnologyFAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523 USA
Re: Kalpha2
Hi, At 04:07 PM 3/28/00 +0100, you wrote: Hi all, On Tue, 28 Mar 2000 16:13:11 +0200, Armel Le Bail wrote: I have a related question about the so-called Kalpha3. Trying to take account of it, I only obtain some slight increase in the Rp and Rwp, though the fit seems to have improved, at first glance. Has someone a powder pattern available which shows clearly Kalpha3, and which he was able to fit by a Rietveld code (which one ?) and obtained some improvement in the Rp and Rwp values ? I have no hints about Kalpha3. But some related hint: Several years ago, we were believing for Kalpha3 or some related satellite lines of the Kalpha doublet really to disturbe our fundamental parameters lines. In the beginning of 1999, we found out the so-called tube-tails (which better should be called focus tails). For example, have a look at www.bgmn.de/tubetails.html ---snip--- This is interesting; I've not seen it (nor have I looked for it). I have been investigating the Kalpha3 matter in the course of the certification of SRMs 640c (silicon) and 660a (LaB6) using the FPA code Topas. I'll reporting on this at EPDIC7. Regards, Jim James P. Cline[EMAIL PROTECTED] Ceramics DivisionVoice (301) 975 5793 National Institute of Standards and TechnologyFAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523 USA
Re: Kalpha2
Hello, At 09:20 PM 3/28/00 +0200, you wrote: On the point of view of theory, can the tube-tails and Kalpha3 satellite explanations be reconciled ? No tube-tails theory in the most recent X-ray powder Diffractometry book from Jenkins and Snyder, only Kalpha1, 2, 3, 4, 5, 6. Don't think so; "Kalpha3" is a component of the emission spectrum of copper while the "tube tails" appears to be an artifact of poor electron beam focusing within the X-ray tube. Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523USA
Re: Kalpha2
Hello II, At 09:20 PM 3/28/00 +0200, you wrote: On the point of view of theory, can the tube-tails and Kalpha3 satellite explanations be reconciled ? No tube-tails theory in the most recent X-ray powder Diffractometry book from Jenkins and Snyder, only Kalpha1, 2, 3, 4, 5, 6. I went back to the "tube tails" web site mentioned by J"org Bergmann: Has anyone done a single crystal rocking curve in an attempt to see these tails? I have just done one to characterize the emission spectrum (as transmitted through a graphite post monochromator). I observed no "tube tails". However, I wasn't looking for them; the crystal was ~27mm in size and scan range for the Si 400 line was 68-70.5 two-theta and the instrument (a D5000) was set up with the smallest divergence and receiving slits and both Soller collimators. These parameters may not be suitable for observance of any (and all) spurious x-rays from the anode. Some geometric exercises may be needed to design an experiment such that any radiation originating from the anode would be diffracted by the single crystal into an anxious detector. The "Kalpha3" is apparent in this scan and its incorporation into the emission spectrum used for an FPA will address the low angle "oddities" shown in the profile of LaB6 (figure a) of the web site. However; the high angle debris remains a problem. Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 National Institute of Standards and Technology FAX (301) 975 5334 100 Bureau Dr. stop 8523 Gaithersburg, MD 20899-8523USA
Re: GSAS profile coefficients
Hi, At 12:27 PM 11/9/98 +1100, you wrote: At 05:24 PM 03-11-98 -0500, you wrote: At 08:26 PM 11/2/98 EST, you wrote: Hi, My questions pertain to refining the profile coefficients. What order do snip1 Thanks MIZ Dear MIZ, The question sounds borring, but is of great importans for everyone, using -snip2 Sr. Petrov Are you suggesting that one tackle the profile fit BEFORE refining atom positions, site occupancies, and thermal parameters? Dr Sue Kesson I have developed and written up a strategy addressing the refinement of profile coefficients for Rietveld analysis of conventional X-ray powder data using GSAS. Its basic premise is the separation of the instrumental terms from the sample related ones and involves the use of SRMs for verification of instrument performance (surprised?). The manuscript is part of an update to the workshop notes distributed at "The Design, Alignment, Calibration and Performance Characteristics of the Conventional Laboratory Diffractometer" presented at Denver last year by myself and Bob Cheary. The manuscript will also appear in a book "Industrial Applications of X-ray Diffraction" edited by D. Smith and F. Chung. I can send the manuscript as a Word97 attachment upon request. I can also sent out an full updated a hardcopy of the workshop notes in about a month as we (Bob and I) are working on an update at this time. Regards, Jim James P. Cline [EMAIL PROTECTED] Ceramics Division Voice (301) 975 5793 A256/223FAX (301) 975 5334 National Institute of Standards and Technology Gaithersburg, MD 20899USA
