Tube tails disturb fundamental parameters models
Hi all, I have added a short discussion about so-called "Tube tails" into the BGMN site. Please see http://www.bgmn.de/device.html#tubetails I cite from this site: >Since the time of our first usage of fundamental parameters profile model, >our measurements are disturbed by so-called "tube tails". Tube tails mean: >A small part of the X-rays emitted by the tube originates not inside the >focus, but up to 1...2cm sideways of the focus. This means 1...2mm equitorial >broadening towards both sides of the optical focus. This tube tails may >totally disturb the profile shapes calculated by fundamental parameters. If someone has experience with those tube tails, too: Please told us. Maybe, tube tails will be discussed in this mailing list. Sincerely Yours J. Bergmann
Re: BaSiF6 or CaSiF6 structures, thanks
Thanks to all for sending me the informations and sorry; I should find by myself the BaSiF6 structure in ICSD, but in reality I look in there for the CaSiF6 or similar structure (ABX6 and tetragonal), so I miss the BaSiF6 and I found some references on it just on the web. In any case thanks for the very fast help, Luca Lutterotti ---Luca Lutterotti Dipartimento di Ingegneria dei Materiali, Universita' di Trento, via Mesiano 77, 38050 Trento, Italy e-mail address : [EMAIL PROTECTED] Home page : http://www.ing.unitn.it/~luttero Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/ Phone number :+39-0461-88-2414 -Fax : +39-0461-88-1977-
Re: BaSiF6 or CaSiF6 structures, thanks
At 10:14 19/11/1999 +0100, you wrote: >Thanks to all for sending me the informations and sorry; I should find >by myself the BaSiF6 structure in ICSD, but in reality I look in there for >the CaSiF6 or similar structure (ABX6 and tetragonal), so I miss the BaSiF6 This is a common error when searching ICSD, so no need to apologise :-) Many people over-restrict their search by specifying too many conditions. In general you should avoid assuming you know the symmetry, or worse the space group. Searching on just ABX6 with 3 elements will give only 157 results, a small enough number to look at; almost all are halides and most are rhombohedral, with only a handful tetragonal. Alan. Alan Hewat, ILL Grenoble, FRANCE <[EMAIL PROTECTED]> tel (33) 4.76.20.72.13 ftp://ftp.ill.fr/pub/dif fax (33) 4.76.20.76.48 http://www.ill.fr/dif/
Re: New member of the rietveld e-list
Dear Edouard, You can try to refine the X parameter that follows U,V,W (FWHM parameters) in the input file for FULLPROF. This will give you another degree of freedom, in the sense that the eta parameter can now increase with 2theta through the equation eta = eta0 + X * 2theta I hope this help you ! Best regards, Claudio. Claudio A. Perottoni Universidade Federal do Rio Grande do Sul Instituto de Fisica - Laboratorio de Altas Pressoes Av. Bento Goncalves, 9500 CAIXA POSTAL 15051 91501-970 PORTO ALEGRE - RS BRAZIL PHONE:55-51-316-6500 FAX :55-51-319-1762 http://www.if.ufrgs.br/~perott/index.html On Fri, 19 Nov 1999, you wrote: > > Dear Rietveld-mailing list users, > As I just subscribed this e-list, let me present myself: > My name is Edouard RENY, and I'm a fresh doctor is material Science > (I obtained my Doctor degree in France this february). Now I'm a post-doc > in Japan working on silicon clathrate structures. > the Rietveld refinement program I use is Fullprof (with a DBWD viewer), > And I have a problem in refining the X-ray peak profiles of one of my samples: > Whatever I do, the refinement leads always to Gaussian type profiles > which we can see on the .prf file, at high 2 teta, don't match at all with > the experimental profile. This sample contains some silicon, and there, no > problem to refine the > peak profiles (even if intensities are not perfect). However at low two > tetas (for 2tetas < 50deg) , > calculated peak shapes match quite well with experimental data. > (see fig1.gif. At higher 2tetas, it's even worse) > I use a PseudoVoigt, it leads usually to eta=0.35 (mixing parameter) > approximatively. > If I fix it to more lorentzienne values (0.6 or 0.8 for instance), > residuals become too high. > U,V, W combination refining converges but if we free eta, > I always finish by having Gaussians peaks mixing the Ka1 and Ka2 > contributions as one peak. > What is strange is that there is no problem for the impurity silicon phase > (peak shapes are > well defined). The profile parameters of the two phases are not commonly > refined. > Has anyone been through this problem? has anyone have an idea of refinement > procedures which would lead to a better peak profile refinement and avoid > this false minimum > where the program always seem to converge? > Thanks in advance for your help > Sincerely > Edouard RENY >
Re: New member of the rietveld e-list
You can also try another peak shape, Thompson-Cox-Hasting pseudo-Voigt (npr=7) is suited is you have broadening from cristallite size or microstrain. you refine U,V,W for Gaussian Component and Y,X for Lorentzian Component. It can be wise not to refine the 5 components simutaneously; first refine U and Y, if it doesn't work try several values of Y and refine U. Moreover check that you don't have anisotropic broadening. Best regards, Patrick WEISBECKER. Laboratoire de Science et Genie des Materiaux metalliques. Ecole des Mines de Nancy > > Dear Edouard, > > You can try to refine the X parameter that follows U,V,W (FWHM >parameters) in the input file for FULLPROF. This will give you another degree >of freedom, in the sense that the eta parameter can now increase with 2theta >throughthe equation > > eta = eta0 + X * 2theta > > I hope this help you ! > > Best regards, > > Claudio. >
Re: weight fractions in GSAS .LST file
Hello all, In my experience GSAS always reports the weght fractions - and their uncertainties - in the .LST file, as long as you have atoms in all the phases, and are refining all but one of the phase fractions under the selection L O S. Has anyone else ever had the problem that Roger is asking about? - Kurt Leinenweber >How do I get GSAS to report weight fractions & their uncertainties in a >.LST file? >Thanks, > >Roger Mason > > * Kurt Leinenweber Dept. of Chemistry Arizona State University Tempe, AZ 85287-1604 Phone (480)-965-8853 Fax (480)-965-0474
