Re: Question on QPA - Amorphous/crystalline mix
Dear Lee: This is interesting to me. Before i take some comments, would you like to send me your data and give me a chance to try. i hope you have done the Rietveld refinement using GSAS. If so, can you send me a package including: 1) recent .exp file; 2) the three .cif file for A, B and corundum. 3) the .ins file describing your instrument parameters. and 4) the GSAS raw data file. If not, please simply send me the upmentioned information without GSAS related format. 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/ Lst. Prof. Loidl and Lunkenheimer Experimental Physics V Center for Electronic Correlations and Magnetism (EKM) University of Augsburg Universitaetsstr. 2 86159 Augsburg Germany http://www.physik.uni-augsburg.de/exp5 - Original Message - From: Lee Gerrard [EMAIL PROTECTED] To: rietveld_l@ill.fr Sent: Tuesday, October 14, 2008 2:20 PM Subject: Question on QPA - Amorphous/crystalline mix I have a question for the list as I know there are a number of people working on QPA. Ok the question is as follows:- We have a mixture of a number of crystalline phases (A and B) and an amorphous (glassy) phase. We can do Rietveld refinement on this and get weight percentage (wt.%) values for the crystalline components. We have added a known amount of corundum as a standard and refined again. Example values we get are as follows:- Phase A 10 wt.% Phase B 50 wt.% Corundum 40 wt.% BUT we know we have added only 33 wt.% corundum - are we able to calculate the wt.% of the amorphous content from the known values? I have tried scaling/ratio'ing the values to the known corundum amount therefore giving:- Phase A 8.25 % Phase B 41.25 % Corundum 33 % TOTAL 82.5 % which leaves 17.5 % left over. Hence must be the amorphous part?? I am not totally convinced by this method at all and would love to know how is best to go about solving this problem. Many thanks, Lee ~~~ Dr. Lee A. Gerrard BSc CChem CSci MRSC Materials Scientist Materials Science Research Division SB40.1 AWE Plc Aldermaston, Reading, Berkshire RG7 4PR Tel: +44 (0)118 982 6516 Fax: +44 (0)118 982 4739 Email: [EMAIL PROTECTED] ~~~
Re: PARST download
Parst seems not a seperated public package any more, but is included in new version of WinGX. http://www.chem.gla.ac.uk/~louis/software/wingx/ 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/ Lst. Prof. Loidl and Lunkenheimer Experimental Physics V Center for Electronic Correlations and Magnetism (EKM) University of Augsburg Universitaetsstr. 2 86159 Augsburg Germany http://www.physik.uni-augsburg.de/exp5 - Original Message - From: [EMAIL PROTECTED] To: Rietveld Method Rietveld_l@ill.fr Sent: Wednesday, August 20, 2008 3:45 PM Subject: PARST download Dear all, can anyone tell me the how can i download the code 'PARST'? thanks in advance prasun
Re: confusion about some GSAS parameters
Hi, friend, Following are my opinions due to my experience, responding to your questions: 1, In principle, POLA should not be refined. To get sensible value of POLA, please just simply consult the technique support of your instrument or ask colleagues who use radiation tubes of the same type. 2, shft and trns parameters suck because they are heavily correlated. To avoid crashing, which occurs frequently when one handles both, it's better disable them and use zero instead. 3, Generally speaking, the profile asymmetry is caused by axial divergence in terms of finite sample and detector sizes. To learn more, please refer this paper: J. Appl. Cryst. (1994). 27, 892-900, by Finger et al. 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/ Lst. Prof. Loidl and Lunkenheimer Experimental Physics V Center for Electronic Correlations and Magnetism (EKM) University of Augsburg Universitaetsstr. 2 86159 Augsburg Germany http://www.physik.uni-augsburg.de/exp5 - Original Message - From: [EMAIL PROTECTED] To: Rietveld Method Rietveld_l@ill.fr Sent: Thursday, August 07, 2008 12:59 PM Subject: confusion about some GSAS parameters Dear all, I am very new with GSAS and some confusions arrised to me during refinement. I will be very much grateful if anyone helps me by giving the explanations of the following facts.. 1. what the parameter POLA stands for(is it polarization factor??)? is it necessary to refine POLA when we are refining the XRD patterns taken by a Brag-Brenteno diffractometer with fixed source? 2. Does 'shft' and 'trns' means sample shift and sample transperancy? what is the difference when we are refining 'zero' in place of refining 'shft' and 'trns'? 3. what physical explanation is behind the asymmetry(refined by 'asym') in the peak shape?
Re: confusion about some GSAS parameters
Dear Dreele: Your response about my comment 1 is convincing which i did not care much about. Thanks for your correction. i appologize to all for this incorrect comment. 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/ Lst. Prof. Loidl and Lunkenheimer Experimental Physics V Center for Electronic Correlations and Magnetism (EKM) University of Augsburg Universitaetsstr. 2 86159 Augsburg Germany http://www.physik.uni-augsburg.de/exp5 - Original Message - From: Robert Von Dreele [EMAIL PROTECTED] To: [EMAIL PROTECTED]; [EMAIL PROTECTED] Sent: Thursday, August 07, 2008 6:08 PM Subject: Re: confusion about some GSAS parameters Hi, The other note on this is not quite correct. POLA is the polarization and depends on choice of monochromator/analyzer angle/material and the wavelength. It is normally not refined but set to known values. Typically for a laboratory instrument with graphite analyzer and CuKa radiation POLA ~0.7 as given in the gsas\example\inst_xry.prm file. For conventional Bragg-Brentano diffractometers the ZERO should NEVER be refined because that is the thing you are setting to zero when you align the diffractometer (or when it gets done by your service rep.) The systematic effect you are seeing is the shift in the sample position away from the diffracting circle; typically on the order of some tens of microns and happens all the time. This is the shft parameter and is appropriate for all but very transparent samples where the expected x-ray penetration is only a few microns, i.e. anything with a metal (Na or above) in it. Refining ZERO instead of shft will bias the resulting lattice parameters because it does not describe the systematic effect correctly. The other parameter trns is only needed for very transparent samples (or harder radiation, e.g. MoKa) where the beam penetration would be many microns. That shifts the effective sample position to be below the surface and thus leads to a shift in peak positions. Different math than for shft but not normally encountered; they are usually mutually exclusive - no need to ever refine both (despite the other remark!). Refinement of both would require a full range scan (to ~140deg 2-theta!); anything less would give very nearly singular refinements probably crazy values for both. By the way the shft parameter has been verified by placing shim stock under the sample; the refined value of shft gave a sample displacement that matched the thickness of the shim. trns has been used to determine sample packing density from the known absorption coefficient for the bulk material. So both are physically meaningful. asym is used in peak shape function #2 in GSAS - I'd recommend using #3 or #4 as those functions are more recent and use a better model for the asymmetry seen at very low scattering angles -see paper by Finger, et al. referenced in GSAS Manual on this. The GSAS Manual does also discuss the other questions you had - I recommend reading it. Best, Bob Von Dreele [EMAIL PROTECTED] wrote: Dear all, I am very new with GSAS and some confusions arrised to me during refinement. I will be very much grateful if anyone helps me by giving the explanations of the following facts.. 1. what the parameter POLA stands for(is it polarization factor??)? is it necessary to refine POLA when we are refining the XRD patterns taken by a Brag-Brenteno diffractometer with fixed source? 2. Does 'shft' and 'trns' means sample shift and sample transperancy? what is the difference when we are refining 'zero' in place of refining 'shft' and 'trns'? 3. what physical explanation is behind the asymmetry(refined by 'asym') in the peak shape?
Re: [sdpd] calibration problems with Silicon+gsas
Hi, All: This morning i tried further refinement work and eventually i got a R value of 0.0518. As a conlusion, the critical steps are summarized: Step 1--origin selection: Thanks to the suggestion from Prof. Gottschalk, i took (1/8,1/8,1/8) origin instead of (0,0,0). It is much improved and it shows the calibration sample has no problem, but current match cannot be better enough. R-0.3578 Step 2--radiation wavelength and pola: Under the suggestion from Prof. Gottschalk, i took the lamda=1.54056 and Pola=0.78989 instead. R-0.2205 Step 3--Release Uiso refinement: after that,R-0.1563 Step 4--Start to refine background parameters. Diffuse scattering was also introduced without refinement(3-type, A=1.0, R=2.352,U=0.005), although it helped not much and neither of ARU can be refined without divergency. R- 0.0518 The current .exp file, as well as related pictures, can also be downloaded via: http://www.physik.uni-augsburg.de/~lujun/ The current R value of 0.0518 is acceptable in average. Our instrument was not so bad. :) Nevertheless, whether the device's state was suitable for refinement analysis or not is still unclear, and i still doubt whether the peakshapes produced by the device can be well descriped by type-3 parameters. i am also doubting whether this rough parameters, as shown below, are somehow reproducible for other materials when all the measurement conditions are the same. Moreover, the background looks quite bad, where the variation of intensities is about 2000, resulting in high chi2 ~ 30! i saw normal background oscillation is about 20-50 and good fitting gives chi2 less than 2. At present, to fix the remaining problem make our refinement in other materials reliable and reasonable, what we plan to do is: 1. optimize the experimental conditions and redo the measurement for silicon several times; 2. buy a new package of standard silicon powder; 3. ask technique supports from the manufacturer of our instrument. Thanks for your attention! Specially thank Prof. from GeoForschungsZentrum Potsdam. We will be engaged to the business of careful instrument calibration in the following weeks. Further comments will still be quite welcomed! By the way, Thanks to kind Prof. Le Bail, our calibration raw data has been tried using FullProff tools. Thoes interested FullProf experts can visit the package via this web page, http://www.physik.uni-augsburg.de/~lujun/Si-fullprof.html. Note: this primary trial is currently without fine structure information(from Prof. Le Bail) 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/ Lst. Prof. Loidl and Lunkenheimer Experimental Physics V Center for Electronic Correlations and Magnetism (EKM) University of Augsburg Universitaetsstr. 2 86159 Augsburg Germany http://www.physik.uni-augsburg.de/exp5 - Original Message - From: Matthias Gottschalk To: [EMAIL PROTECTED] Sent: Tuesday, June 10, 2008 7:39 PM Subject: Re: [sdpd] calibration problems with Silicon+gsas Ok, just as I thought. It is the wrong atom position. 0 0 0 has in the default origin setting a multiplicity of 16 and not 8. So put the Si on 1/8 1/8 1/8 and then all will work. Some additional remarks. 1. Set POLA to 0.78989 because you have probably a primary monochromator, too. 2. Set the wavelength to 1.54056 3. Use the profile function 2 4. Write an parameter file (using EXPGUI) for your Stadi P which also includes the GU, GV, GW, LX, and GY parameters refied for this sample. Only use these parameters. 5. To get a meaningful Durbin-Watson factor your intensities are to high. For a cubic phase use maximum intensities in the order of 1 (8000-1) to get reasonable statistics and esd`s. 6. Use difuse scattering for your background. Matthias Gottschalk On Tue, 10 Jun 2008 19:05:35 +0200 [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Hello again, everyone: i have just received a reply from Prof. Stephens, indicating some problems about the attachment. i am so sorry for this convenience, but i bet i did not intend to do something bad. To solve this problem, i have created a public webpage for my questions. If anyone still has interest please visit: http://www.physik.uni-augsburg.de/~lujun/ Anyway, the attention raised by Prof. Stephens should be heartly appreciated. :) 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/ Lst. Prof. Loidl and Lunkenheimer Experimental Physics V Center for Electronic Correlations and Magnetism (EKM) University of Augsburg Universitaetsstr. 2 86159
Re: FullProf problem in R3m
Dear Stanislav: a triviality, but are you using the right wavelength in FullProf? are cell parameters updated (the right ones)? sorry for the banality, and good luck, marco - Original Message Follows - From: Stanislav Ferdov [EMAIL PROTECTED] To: rietveld_l@ill.fr Subject: FullProf problem in R3m Date: Fri, 18 Aug 2006 08:33:38 -0700 (PDT) Dear All, I am trying to refine a rombohedral phase with space group R3m. The problem comes when I type the space group and cell parameters in FullProf and try to fit the powder pattern the program does not generate the powder XRD reflections on the right 2 theta positions (no match between the calculated and experimental file). When I use PowderCell the calculated and experimental files match perfectly. Has somebody faced such a problem and what could be the solution. Many thanks in advance! __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Marco Sommariva -- Marco Sommariva Department of Materials Science University Milano-Bicocca Via R. Cozzi 53, 20125 Milano (ITALY) mail: [EMAIL PROTECTED] phone: 0039.02.64.48.51.41 fax: 0039.02.64.48.54.00 --
Re: hexagonal system in FullProf
Thanks a lot!! Regards, marco - Original Message Follows - From: [EMAIL PROTECTED] To: rietveld_l@ill.fr Date: Tue, 13 Jun 2006 18:55:02 +0200 Dear Marco, The automatic mode of Fullprof does it better than you would do in manual mode. See for an explanation the following page on CCP14: http://www.ccp14.ac.uk/tutorial/fullprof/hexagonal_rhom_n ot_120degrees.html regards, Arie Quoting [EMAIL PROTECTED] [EMAIL PROTECTED]: Dear FullProf Users, could I ask you why during refinement of an hexagonal structure with FullProf in automatic refinement mode (Aut=1) the program sets the same refinement code for both lattice parameter a and for gamma(=120°) ? Thanks in advance, marco Marco Sommariva -- Marco Sommariva Department of Materials Science University Milano-Bicocca Via R. Cozzi 53, 20125 Milano (ITALY) mail: [EMAIL PROTECTED] phone: 0039.02.64.48.51.41 fax: 0039.02.64.48.54.00 -- -- -- This message was sent using IMP, the Internet Messaging Program.
Structure dissemination
Sorry, I had read the querelle about forwarding of papers, not yet about structure. Regards, marco - Original Message Follows - From: Shankland, K \(Kenneth\) [EMAIL PROTECTED] To: rietveld_l@ill.fr Date: Wed, 7 Jun 2006 08:56:31 +0100 I'm sure this issue comes up time and time again, but isn't it true to say that the mailing list is not the place to be posting structural entries from proprietary databases? The Terms and conditions for the ICSD http://www.fiz-karlsruhe.de/ecid/Internet/en/agb/icsd.html would appear to prohibit this type of activity. Regards, Kenneth Marco Sommariva -- Marco Sommariva Department of Materials Science University Milano-Bicocca Via R. Cozzi 53, 20125 Milano (ITALY) mail: [EMAIL PROTECTED] phone: 0039.02.64.48.51.41 fax: 0039.02.64.48.54.00 --
Re: how to find Polarization
Dear All, if I well understood JFC correction is perfect in case of parallel incident beam; so, in case of conventional Bragg-Brentano diffractometer, shouldn't it work well only in case of use of Goebel Mirrors, that get incident beam exactly parallel? And is it true that using Goebel Mirrors and sample in capillary (Debye-Scherrer) gets intensity values more realistic than on a conventional Bragg-Brentano geometry? Thanks in advance, marco Marco Sommariva -- Marco Sommariva Department of Materials Science University Milano-Bicocca Via R. Cozzi 53, 20125 Milano (ITALY) mail: [EMAIL PROTECTED] phone: 0039.02.64.48.51.41 fax: 0039.02.64.48.54.00 --
superstructure peak
Dear Crystallographers, I have a problem with the refinement of a structure in which both sharp and broadened peaks appear in the neutron powder diffraction profile. The broadening of low intensity peaks is probably due to the existence of a supestructure. To my knowledge in GSAS it's not possible to perform the structural refinement of the same phase with two kinds of profile model functions, one for sharp peaks and the other for broadened peaks (I already saw that the function n.4 by Stephens doesn't match my case). Does anybody can suggest me some other softwares (possibly free) to solve my problem? Thanks in advance, regards Marco Sommariva
how much is too much?
Dear Rietvelders, I am working on a structure of a ferric sulfate, with triclinic symmetry and 50 atoms in the unit cell. We have both X-ray synchrotron and neutron data. At the moment, I am using constraints to keep the O-H bond distances and H-O-H angles within reasonable range. One of the metal sites contains vacancies (2/3 occupied, 1/3 vacant), but the ligands (H2O) remain even if the metal is absent. As expected, the atoms of these water molecules have very high thermal factors, indicating split positions. The presence of vacancies also changes the hydrogen bonding scheme around this site. We have ab initio calculations explaining nicely what is going on on this position. My question is: Since I am already using the constraints, therefore somewhat imposing my solution on the structure, can I add more complexity to the refinement, using the results of ab initio calculations, and say that this is real? Or should I just be happy with the high thermal factors and the explanation from the calculations? Is there a way to know that the data are not providing any more results, and you are just forcing the outcome you like? Thank you for the answers, Juro Majzlan Juro Majzlan Department of Geosciences Princeton University Princeton, New Jersey 08544 USA
Fe75Si15B10diffraction pattern
Dear all, I am interesting in the synthesis of the crystallization of amorphous Fe75Si15B10 produced by high energy ball milling. My results obtained using in situ 57Fe Mössbauer (MS) measurements at 825 K, show the possible presence of Fe5SiB2.I need information about crystal structure of Fe5SiB2. Any help regarding this will be appreciated Thank you Justiniano Justiniano Quispe M. Universidad Nacional Mayor de San Marcos Facultad de Ciencias Físicas Laboratorio de Espectroscopia Mössbauer P.O. Box 14-0149. Lima. Peru Telefax: +51 1 452 1343 Lima - Perú
No Subject
I have refined a structure at different temperatures (10-300K). The lattice constant increases with increasing temperature. At low temperature (below 50K) the variation is not linear. In some papers , I have read that a simple Debye model is sufficient to fit this behavior. Is is correst? In this case, could you please send me the exact function to permform the fit. Thanks in advance. Sincerely, Laurent CHAPON LPMC, UMR 5617 CNRS, CC003 Université Montpellier II 5, place E. Bataillon 34095 Montpellier Cedex FRANCE Mail to : [EMAIL PROTECTED] Phone :+33-4-67-14-48-88 (ask for Mr CHAPON) Fax: +33-4-67-14-42-90
Bonds calculations....
Does anyone can provide me a software to calculate bonds and angles in crystal structure (input: space group , atomic positions and unit cell parameter). Thanks. Laurent CHAPON LPMC, UMR 5617 CNRS, CC003 Université Montpellier II 5, place E. Bataillon 34095 Montpellier Cedex FRANCE Mail to : [EMAIL PROTECTED] Phone :+33-4-67-14-48-88 (ask for Mr CHAPON)
Fe-Si DO3 atomic positions
Hi everyone I need some help with the atomic positions for the Fe-Si DO3 structure. Can anyone help me? Thanks and happy new year. Regards Jim [JIM FLORES[[EMAIL PROTECTED]]]
