GSAS RF2?
Dear GSAS users, first of all Good Easter to everybody (even if quite late!). I have a problem with GSAS: I don't understand why, during a refinement of a TOF neutron profile, I see a big increase of the Bragg index RF^2 (from 12% to 61% !!) if I insert in the refinement just three little peaks (i.e. if I start my histogram from 0.67 instead from 0.7 Angstrom). Profile indexes Rp and wRp remains the same, as these 3 peaks are well fitted by the tetragonal symmetry chosen !! So they don't belong to an impurity, and space group seems right! I don't have many peaks, so I would like to use also these peaks in the refinement. Another little question: which convergence criterion do you think it's better for a normal Rietveld refinement? In Expgui the default value is fixed to 0.01, but I read it could be bigger but less than 0.10. Thanks a lot in advance, marco -- Marco Sommariva Department of Materials Science University of Milano - Bicocca Via R. Cozzi 53 - 20125 MILAN, ITALY Phone +39.02.6448.5141 (5142) Fax +39.02.6448.5400 e-mail: [EMAIL PROTECTED]
Re: CIFs for powder diffraction/Software testing
Dear All, I`m trying to refine the synchrotron data of BaTiO3 powder. In my case, i believe that Ti has two valance states, 3+ and 4+. Since the x rays are scattered from the electrons, Ti 3+ and Ti 4+ should act as different scatterers. I want to add both Ti 3+ and Ti 4+ to the lattice. I think, when i add the Ti atoms to the lattice, it is treated as Ti 4+. Is there a way to add Ti 3+ ions to the lattice? Or my argument does not make any sense? Happy Refinements Vahit = Vahit Atakan Ph.D student Rutgers, The State University of New Jersey Department of Ceramic and Materials Science & Engineering Room CCR 143 607 Taylor Road Piscataway, NJ 08855-0909 732-445-5564 732-445-6264 (fax) [EMAIL PROTECTED] -Original Message- From: Brian H. Toby [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 02, 2005 4:06 PM To: rietveld_l@ill.fr Brian H. Toby wrote: > At present, to my knowledge, there is exactly one program that can be > used to read & plot powder diffraction data from these CIFs: pdCIFplot This turns out to be wrong. CMPR can also do this (http://www.ncnr.nist.gov/xtal/software/cmpr/). My apologies to the author of that program. Brian
RE: Size Strain In GSAS
Leonid, > Could you, please, give a reference to a study where Dv and Da sizes > were derived from the parameters of pseudo-Voight or Voight fitted to > simulated profiles for various size distribution dispersions? I did something better (I hope).. at the end of the mesg you find xy data with a simulation: Ceria (Fm-3m), CuKa 0.15406 nm (delta function, i.e. no emission profile aberration)), size broadening due to a lognormal distribution of spheres only, no background, no noise, no Lorentz-Polarization, no aberrations of any kind. Peaks present in the pattern: 111 200 220 311 222 400 331 420 422 333/511 fitted but not used in the analysis as they have same d. Simulation done using WPPM, or, simply, taking the FT of the formulae proposed in Acta Cryst (2002) A58, 190-200 for the lognorm. The program used for the simulation allows fully recovery of the original parameters, starting from different initial values (self consistent check..). Analysis done using traditional "peak fitting" Williamson-Hall and Warren-Averbach methods, applying the formulae found e.g. on Phil Mag (1998) A77 [3], 621-640 to obtain the lognorm from the and values (should the ref be unavailable, they can be easily calculated, or I can also provide the formulae). I can send the simulation parameters and all plots/calculations I did to the interested members (just drop me a line). Results of WH and WA seems "good" but the distributions they provide are completely out with respect to the true one (unless I did some mistake, but that can be easily checked). I could have attached the results file here, but I'm sure Alan (as list moderator) would haven't been quite happy about attachments. Happy calculation, for those who wants to do the analysis by themselves without knowing the result in advance! Mat - Matteo Leoni, PhD Department of Materials Engineering and Industrial Technologies University of Trento 38050 Mesiano (TN) ITALY SIMULATED DATA in xy (2theta Intensity) format. 1.80e+001 4.470421e+000 1.806000e+001 4.513074e+000 1.812000e+001 4.556395e+000 1.818000e+001 4.600401e+000 1.824000e+001 4.645108e+000 1.83e+001 4.690529e+000 1.836000e+001 4.736682e+000 1.842000e+001 4.783659e+000 1.848000e+001 4.831332e+000 1.854000e+001 4.879787e+000 1.86e+001 4.929045e+000 1.866000e+001 4.979123e+000 1.872000e+001 5.030047e+000 1.878000e+001 5.081826e+000 1.884000e+001 5.134484e+000 1.89e+001 5.188043e+000 1.896000e+001 5.242526e+000 1.902000e+001 5.297955e+000 1.908000e+001 5.354352e+000 1.914000e+001 5.411743e+000 1.92e+001 5.470151e+000 1.926000e+001 5.529602e+000 1.932000e+001 5.590123e+000 1.938000e+001 5.651740e+000 1.944000e+001 5.714484e+000 1.95e+001 5.778379e+000 1.956000e+001 5.843577e+000 1.962000e+001 5.909879e+000 1.968000e+001 5.977428e+000 1.974000e+001 6.046257e+000 1.98e+001 6.116400e+000 1.986000e+001 6.187892e+000 1.992000e+001 6.260770e+000 1.998000e+001 6.335082e+000 2.004000e+001 6.410849e+000 2.01e+001 6.488118e+000 2.016000e+001 6.566933e+000 2.022000e+001 6.647338e+000 2.028000e+001 6.729377e+000 2.034000e+001 6.813098e+000 2.04e+001 6.898548e+000 2.046000e+001 6.985779e+000 2.052000e+001 7.074842e+000 2.058000e+001 7.165793e+000 2.064000e+001 7.258687e+000 2.07e+001 7.353585e+000 2.076000e+001 7.450544e+000 2.082000e+001 7.549629e+000 2.088000e+001 7.650906e+000 2.094000e+001 7.754684e+000 2.10e+001 7.860571e+000 2.106000e+001 7.968865e+000 2.112000e+001 8.079643e+000 2.118000e+001 8.192986e+000 2.124000e+001 8.308978e+000 2.13e+001 8.427707e+000 2.136000e+001 8.549279e+000 2.142000e+001 8.673760e+000 2.148000e+001 8.801265e+000 2.154000e+001 8.931897e+000 2.16e+001 9.065765e+000 2.166000e+001 9.202984e+000 2.172000e+001 9.343672e+000 2.178000e+001 9.487954e+000 2.184000e+001 9.635962e+000 2.19e+001 9.787833e+000 2.196000e+001 9.943709e+000 2.202000e+001 1.010374e+001 2.208000e+001 1.026809e+001 2.214000e+001 1.043692e+001 2.22e+001 1.061041e+001 2.226000e+001 1.078874e+001 2.232000e+001 1.097211e+001 2.238000e+001 1.116071e+001 2.244000e+001 1.135477e+001 2.25e+001 1.155511e+001 2.256000e+001 1.176082e+001 2.262000e+001 1.197270e+001 2.268000e+001 1.219102e+001 2.274000e+001 1.241607e+001 2.28e+001 1.264814e+001 2.286000e+001 1.288756e+001 2.292000e+001 1.313466e+001 2.298000e+001 1.338978e+001 2.304000e+001 1.365333e+001 2.31e+001 1.392571e+001 2.316000e+001 1.420732e+001 2.322000e+001 1.449861e+001 2.328000e+001 1.480009e+001 2.334000e+001 1.511227e+001 2.34e+001 1.543569e+001 2.346000e+001 1.577095e+001 2.352000e+001 1.611867e+001 2.358000e+001 1.647952e+001 2.364000e+001 1.685423e+001 2.37e+001 1.724355e+001 2.376000e+001 1.764832e+001 2.382000e+001 1.806942e+001 2.388000
RE: Size Strain In GSAS
Dear Matteo, Thanks for the exercise. >From pseudo-Voight fitting I have got Dv=33A, Da=23A, which gives the average size =21A and the relative dispersion c=0.28 (c = [sigma/]^2). However, I suspect that the actual values you used for the simulation were ~30A and c~0.25. Do I win the F1 GP? :-) Actually, I have also played with simulated profiles for various dispersions and I am going to calibrate the calculations of Dv and Da from pseudo-Voight. Hope I will include these calibrated calculations to the next release of DDM. Cheers, Leonid P.S. As for a Ferrari powered by a John Deere tractor engine, I believe that none of us would win a F1 GP even with an original Ferrari engine. I have better recipe: take a Russian tank T-72 (which is simpler and cheaper than Ferrari), put it at the pole-position, turn the gun back and enjoy driving - F1 GP is guaranteed. __ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/
Re: Change format
Good afternoon, Now I haven't ConvX here, but once I had done so: you can copy angle and Intensity columns from UXD file on a NotePad (Block Notes), saving it as a file *.txt. Then with ConvX you convert this simple ASCII file (select file ASCII, 2theta/Intensity) in a file for GSAS (type file: GSAS). I had tried to convert a UXD file but it didn't work. You can try this way. Good luck, marco! Il mer, 2005-03-30 alle 17:30, [EMAIL PROTECTED] ha scritto: > Hello > > I am a new user of GSAS, but I have a problem. > > I can't to convert my files to the GSAS format. I trying with powder and > convx software, but I don't have good results. I trying with the option > "convert" in GSAS, but nothing, too. > > I send you one file (attache to this message). Please, tell me how I can > to convert this file. > > Please, tell me what kind of information I should write in the first raw, > too. > > > > Sincerely -- Marco Sommariva Department of Materials Science University of Milano - Bicocca Via R. Cozzi 53 - 20125 MILAN, ITALY Phone +39.02.6448.5141 (5142) Fax +39.02.6448.5400 e-mail: [EMAIL PROTECTED]
RE: Size Strain In GSAS
Dear Matteo, Thanks for the problem. I have used pseudo voigt function to fit the peaks and finally used the program BREADTH and obtained Dv=31 A, Da=18 A. Please send me your simulation parameters, plots/calculations. 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: Matteo Leoni <[EMAIL PROTECTED]> Date: Wednesday, March 30, 2005 4:39 pm --- Begin Message --- Leonid, > Could you, please, give a reference to a study where Dv and Da sizes > were derived from the parameters of pseudo-Voight or Voight fitted to > simulated profiles for various size distribution dispersions? I did something better (I hope).. at the end of the mesg you find xy data with a simulation: Ceria (Fm-3m), CuKa 0.15406 nm (delta function, i.e. no emission profile aberration)), size broadening due to a lognormal distribution of spheres only, no background, no noise, no Lorentz-Polarization, no aberrations of any kind. Peaks present in the pattern: 111 200 220 311 222 400 331 420 422 333/511 fitted but not used in the analysis as they have same d. Simulation done using WPPM, or, simply, taking the FT of the formulae proposed in Acta Cryst (2002) A58, 190-200 for the lognorm. The program used for the simulation allows fully recovery of the original parameters, starting from different initial values (self consistent check..). Analysis done using traditional "peak fitting" Williamson-Hall and Warren-Averbach methods, applying the formulae found e.g. on Phil Mag (1998) A77 [3], 621-640 to obtain the lognorm from the and values (should the ref be unavailable, they can be easily calculated, or I can also provide the formulae). I can send the simulation parameters and all plots/calculations I did to the interested members (just drop me a line). Results of WH and WA seems "good" but the distributions they provide are completely out with respect to the true one (unless I did some mistake, but that can be easily checked). I could have attached the results file here, but I'm sure Alan (as list moderator) would haven't been quite happy about attachments. Happy calculation, for those who wants to do the analysis by themselves without knowing the result in advance! Mat - Matteo Leoni, PhD Department of Materials Engineering and Industrial Technologies University of Trento 38050 Mesiano (TN) ITALY SIMULATED DATA in xy (2theta Intensity) format. 1.80e+001 4.470421e+000 1.806000e+001 4.513074e+000 1.812000e+001 4.556395e+000 1.818000e+001 4.600401e+000 1.824000e+001 4.645108e+000 1.83e+001 4.690529e+000 1.836000e+001 4.736682e+000 1.842000e+001 4.783659e+000 1.848000e+001 4.831332e+000 1.854000e+001 4.879787e+000 1.86e+001 4.929045e+000 1.866000e+001 4.979123e+000 1.872000e+001 5.030047e+000 1.878000e+001 5.081826e+000 1.884000e+001 5.134484e+000 1.89e+001 5.188043e+000 1.896000e+001 5.242526e+000 1.902000e+001 5.297955e+000 1.908000e+001 5.354352e+000 1.914000e+001 5.411743e+000 1.92e+001 5.470151e+000 1.926000e+001 5.529602e+000 1.932000e+001 5.590123e+000 1.938000e+001 5.651740e+000 1.944000e+001 5.714484e+000 1.95e+001 5.778379e+000 1.956000e+001 5.843577e+000 1.962000e+001 5.909879e+000 1.968000e+001 5.977428e+000 1.974000e+001 6.046257e+000 1.98e+001 6.116400e+000 1.986000e+001 6.187892e+000 1.992000e+001 6.260770e+000 1.998000e+001 6.335082e+000 2.004000e+001 6.410849e+000 2.01e+001 6.488118e+000 2.016000e+001 6.566933e+000 2.022000e+001 6.647338e+000 2.028000e+001 6.729377e+000 2.034000e+001 6.813098e+000 2.04e+001 6.898548e+000 2.046000e+001 6.985779e+000 2.052000e+001 7.074842e+000 2.058000e+001 7.165793e+000 2.064000e+001 7.258687e+000 2.07e+001 7.353585e+000 2.076000e+001 7.450544e+000 2.082000e+001 7.549629e+000 2.088000e+001 7.650906e+000 2.094000e+001 7.754684e+000 2.10e+001 7.860571e+000 2.106000e+001 7.968865e+000 2.112000e+001 8.079643e+000 2.118000e+001 8.192986e+000 2.124000e+001 8.308978e+000 2.13e+001 8.427707e+000 2.136000e+001 8.549279e+000 2.142000e+001 8.673760e+000 2.148000e+001 8.801265e+000 2.154000e+001 8.931897e+000 2.16e+001 9.065765e+000 2.166000e+001 9.202984e+000 2.172000e+001 9.343672e+000 2.178000e+001 9.487954e+000 2.184000e+001 9.635962e+000 2.19e+001 9.787833e+000 2.196000e+001 9.943709e+000 2.202000e+001 1.010374e+001 2.208000e+001 1.026809e+001 2.214000e+001 1.043692e+001 2.22e+001 1.061041e+001 2.226000e+001 1.078874e+001 2.232000e+001 1.097211e+001 2.238000e+001 1.116071e+001 2.244000e+001 1.135477e+001 2.25e+001 1.155511e+001 2.256000e+001 1.176082e+001 2.262000e+001 1.197270e+001
Change format
P.S. Attachment is not allowed in this list. I am using powder to convert files and using well in GSAS. Use Powder and click open file - chose the option with your extention. Then save the file as *.gsa. It should work. 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: [EMAIL PROTECTED] Date: Wednesday, March 30, 2005 9:00 pm > Hello > > I am a new user of GSAS, but I have a problem. > > I can't to convert my files to the GSAS format. I trying with > powder and > convx software, but I don't have good results. I trying with the > option"convert" in GSAS, but nothing, too. > > I send you one file (attache to this message). Please, tell me how > I can > to convert this file. > > Please, tell me what kind of information I should write in the > first raw, > too. > > > > Sincerely > >
Re: Change format
your data are free format with intensities as a real variable. Using
excel or any equivalent you can convert in integer intensities (e.g.
multiplying by ten to avoid errors with low values) which is the usual
data input ("counts").
Step 2 is then to convert the free 2th-I (real-integer) file into GSAS
format (no 2th, 10 int per line) using any of the conversion programs.
The last step is to run the convert of GSAS which is to make the file
random access (you'll see no difference of format with notepad).
Hope this helps
miguel
BTW, don't send attachments on the mail list, a couple of lines
pasted in the mail would have been sufficient!
On 30 Mar 2005 at 10:30, [EMAIL PROTECTED] wrote:
> Hello
>
> I am a new user of GSAS, but I have a problem.
>
> I can't to convert my files to the GSAS format. I trying with powder
> and convx software, but I don't have good results. I trying with the
> option "convert" in GSAS, but nothing, too.
>
> I send you one file (attache to this message). Please, tell me how I
> can to convert this file.
>
> Please, tell me what kind of information I should write in the first
> raw, too.
>
>
>
> Sincerely
>
>
--
Miguel Gregorkiewitz
Dip Scienze della Terra, Università
via Laterino 8, I-53100 Siena, Europe
fon +39'0577'233810 fax 233938
email [EMAIL PROTECTED]
Re: Change format
your data are free format with intensities as a real variable. Using
excel or any equivalent you can convert in integer intensities (e.g.
multiplying by ten to avoid errors with low values) which is the usual
data input ("counts").
Step 2 is then to convert the free 2th-I (real-integer) file into GSAS
format (no 2th, 10 int per line) using any of the conversion programs.
If the numbers are real values then they are not counts. They may be
counts per second or something else. One needs to have uncertainty
estimates for these intensities before one can do a meaningful Rietveld
refinement (with any code). Following the above procedure, by
multiplying them by an arbitrary constant and then inputting them to
GSAS as if they were counts will cause GSAS to compute the
uncertainties as the square-root of the intensities, something that is
quite unlikely to be true. This will cause the refinement to be
weighted improperly and the "r-factors" to be wrong.
I can sympathize with the temptation to skip the details (like
understanding exactly what your data represent) to "get on with the
science," but the eventual result is a study that is not suitable for
publication.
Brian
Re: Change format
[EMAIL PROTECTED] a écrit : Hello I am a new user of GSAS, but I have a problem. I can't to convert my files to the GSAS format. I trying with powder and convx software, but I don't have good results. I trying with the option "convert" in GSAS, but nothing, too. I send you one file (attache to this message). Please, tell me how I can to convert this file. Please, tell me what kind of information I should write in the first raw, too. Hi By looking at the file one can see that you have three lines with negative intensities, at the end of the file. By removing these you can read the file with Open/Ascii XY by using Powder4 and probably any other program. Regards
Re: Change format
Brian Toby a écrit : If the numbers are real values then they are not counts. They may be counts per second or something else. One needs to have uncertainty estimates for these intensities before one can do a meaningful Rietveld refinement (with any code). Following the above procedure, by multiplying them by an arbitrary constant and then inputting them to GSAS as if they were counts will cause GSAS to compute the uncertainties as the square-root of the intensities, something that is quite unlikely to be true. This will cause the refinement to be weighted improperly and the "r-factors" to be wrong. Hi That's right. However, one can get something like 'real counts' if we measure several times and "merge" the data. Of course in this case you have the esd's and one should use it ! In Powder the "real" counts are converted to the nearest integer for the conversion to GSAS and other programs. Regards PS As for the attachement to the list, for this particular case it was important to have the whole file to spot the problem. I often get info for bugs in Powder4 and while I am sure there are plenty of them -at least a pair- most of the reported problems are actually data files with problems. So guys, look at the data files first (with PFE or Notepad) then try to convert them.
