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To: [email protected] From: Armel Le Bail [[email protected]] Mailing-List: list [email protected]; contact [email protected] List-Unsubscribe: [mailto:[email protected]] Date: Tue, 06 Jun 2000 09:20:09 +0200 Reply-To: [email protected] Subject: [sdpd] Reference materials for calibration and indexing Hi, The latest addition into PowBase is In2O3, cubic variety (a=10.119 A; space group Ia3). http://sdpd.univ-lemans.fr/powbase/ This compound would be a nice reference material to be mixed with your unknown sample for indexing. No preferred orientation occured on a sample from CERAC Inc. The minimal FWHM is near of 0.06� (2-theta), without annealing. Unfortunately, 3 of the 7 first reflections are very weak. Anyway, this material may replace NAC (Na2Ca3Al2F14) if you need a more absorbing sample. Other suggestions of inexpensive reference materials welcome. Best, Armel Le Bail http://sdpd.univ-lemans.fr/course/ Armel Le Bail - Universite du Maine, Laboratoire des Fluorures, CNRS ESA 6010, Av. O. Messiaen, 72085 Le Mans Cedex 9, France http://www.cristal.org/ |
From: "Yokochi, Alexandre" [[email protected]] Mailing-List: list [email protected]; contact [email protected] Delivered-To: mailing list [email protected] Date: Tue, 6 Jun 2000 09:28:04 -0700 Reply-To: [email protected] Subject: [sdpd] RE: Reference materials for calibration and indexing Armel, The suggestion of In2O3 is very welcome. I too have struggled with finding a good calibration standard. For reflection mode I have hit on ZrW2O8, cubic, P2(1)3 (at r.t.) or P a -3 (at 150 C or higher), with a = 9.1567 (at r.t.) and has well characterized thermal expansion behaviour (as studied by neutron diffraction). Much higher linear absorption coefficient than NAC too, which is nice for reflection mode. Cheers, AlexY Dr. Alexandre F. T. Yokochi Assistant Professor (Senior Research) Director, X-ray Crystallographic Facilities Department of Chemistry Oregon State University Corvallis, OR 97331-4003 Ph# (541) 737-6724 Email: [email protected] Fax# (541) 737-2062 Web Page: crystal.chem.orst.edu/~alexy (temporarily unavailable) |
From: Lachlan Cranswick [[email protected]] Mailing-List: list [email protected]; contact [email protected] Delivered-To: mailing list [email protected] Date: Tue, 06 Jun 2000 17:51:21 +0100 Reply-To: [email protected] Subject: Re: [sdpd] Reference materials for calibration and indexing >The latest addition into PowBase is In2O3, cubic >variety (a=10.119 A; space group Ia3). > >http://sdpd.univ-lemans.fr/powbase/ > >This compound would be a nice reference material to be mixed >with your unknown sample for indexing. No preferred >orientation occured on a sample from CERAC Inc. >The minimal FWHM is near of 0.06� (2-theta), without >annealing. Unfortunately, 3 of the 7 first reflections are very >weak. Anyway, this material may replace NAC (Na2Ca3Al2F14) >if you need a more absorbing sample. > >Other suggestions of inexpensive reference materials welcome. While the above implies it can be used out of the bottle(?): Does In2O3 "need" any annealing or can it be used reliably out of the bottle? Also, what is the general cost for 10 to 100 grams? ---- Is it possible to get a "fixed" slit data collection of this where all the slit and geometry settings are noted? I would be quite eager to try out a Fundamental Parameters fit using Koalariet/XFIT. I am quite a fan of Ian Madsen's suggestion of using annealed cubic Y2O3. Except you normally have to anneal it yourself. This is 10.6 A IA3 cubic. This has performed well in the past using Fundamental Parameters fitting to look at diffractometer geometry and alignment. Lachlan. Lachlan M. D. Cranswick Collaborative Computational Project No 14 (CCP14) for Single Crystal and Powder Diffraction Daresbury Laboratory, Warrington, WA4 4AD U.K Tel: +44-1925-603703 Fax: +44-1925-603124 E-mail: [email protected] Ext: 3703 Room C14 http://www.ccp14.ac.uk |
From: Armel Le Bail [[email protected]] Mailing-List: list [email protected]; contact [email protected] Delivered-To: mailing list [email protected] Date: Tue, 06 Jun 2000 20:08:34 +0200 Reply-To: [email protected] Subject: Re: [sdpd] Reference materials for calibration and indexing >While the above implies it can be used out of the bottle(?): >Does In2O3 "need" any annealing or can it be used reliably >out of the bottle? Also, what is the general cost for 10 to >100 grams? Some annealing seems necessary if you compare the FWHMs (� 2-theta) of In2O3 and CeO2 recently distributed by D. Balzar for his Size/strain Round Robin (recorded in "exactly" the same conditions). There is one Y2O3 too in Powbase, not annealed. Also is given an Y2O3-a got with the Koalariet package, probably annealed (?) : In2O3 CeO2 2-theta Y2O3 Y2O3-a 0.061 0.056 30.5 0.104 0.112 0.076 0.060 51.0 0.111 0.107 0.092 0.064 69.4 0.124 0.106 0.116 0.071 89.8 0.147 0.114 0.150 0.084 110.1 0.190 0.140 0.207 0.110 130.2 0.260 About the cost, I have no catalog at home ;-). >Is it possible to get a "fixed" slit data collection of this >where all the slit and geometry settings are noted? Recording conditions were : Bragg Brentano geometry, Cu-Kalpha, graphite monochromator in the diffracted beam, Soller 2�, variable slits ensuring a constant 6mm illumination of the sample surface, Soller 2�, receiving slit 0.1mm. The pattern in PowBase is corrected by 1/(sin theta) and so is already equivalent to a "fixed" slit data collection. >I would be quite eager to try out a Fundamental Parameters >fit using Koalariet/XFIT. Why exactly the FP approach cannot deal with that variable slits geometry ? Armel Armel Le Bail - Universit� du Maine, Laboratoire des Fluorures, CNRS ESA 6010, Av. O. Messiaen, 72085 Le Mans Cedex 9, France http://www.cristal.org/ |
From: [email protected] Mailing-List: list [email protected]; contact [email protected] Delivered-To: mailing list [email protected] Date: Tue, 6 Jun 2000 19:26:53 +0100 (BST) Reply-To: [email protected] Subject: Re: [sdpd] Reference materials for calibration and indexing > Some annealing seems necessary if you compare the > FWHMs (� 2-theta) of In2O3 and CeO2 recently distributed by > D. Balzar for his Size/strain Round Robin (recorded in "exactly" > the same conditions). There is one Y2O3 too in Powbase, not > annealed. Also is given an Y2O3-a got with the Koalariet package, > probably annealed (?) : > > In2O3 CeO2 2-theta Y2O3 Y2O3-a > 0.061 0.056 30.5 0.104 0.112 > 0.076 0.060 51.0 0.111 0.107 > 0.092 0.064 69.4 0.124 0.106 > 0.116 0.071 89.8 0.147 0.114 > 0.150 0.084 110.1 0.190 0.140 > 0.207 0.110 130.2 0.260 The Y2O3 is annealed (1200 C for around two to three days?) - according to the equations of XFIT/Koalariet it has near zero strain and around 3000 Angstrom average crystallite size. It can refine on the common slit settings quite accurately which is the thing that interests me. What is the average size/strain results determined on the In2O3 or is this what the round robin will give? > >Is it possible to get a "fixed" slit data collection of this > >where all the slit and geometry settings are noted? > > Recording conditions were : Bragg Brentano geometry, Cu-Kalpha, > graphite monochromator in the diffracted beam, Soller 2�, variable > slits ensuring a constant 6mm illumination of the sample surface, > Soller 2�, receiving slit 0.1mm. The pattern in PowBase is corrected > by 1/(sin theta) and so is already equivalent to a "fixed" slit data collection. > > >I would be quite eager to try out a Fundamental Parameters > >fit using Koalariet/XFIT. > > Why exactly the FP approach cannot deal with that variable > slits geometry ? Sorry - forgot that it can - matter of habit in using fixed slit. XFIT can do Variable slit (not really used it) - but old biases against variable slits die hard. Lachlan. -- Lachlan M. D. Cranswick Collaborative Computational Project No 14 (CCP14) for Single Crystal and Powder Diffraction Daresbury Laboratory, Warrington, WA4 4AD U.K Tel: +44-1925-603703 Fax: +44-1925-603124 E-mail: [email protected] Ext: 3703 Room C14 http://www.ccp14.ac.uk |
From: [email protected] Mailing-List: list [email protected]; contact [email protected] Delivered-To: mailing list [email protected] Date: Tue, 6 Jun 2000 20:01:16 +0100 (BST) Reply-To: [email protected] Subject: Re: [sdpd] Reference materials for calibration and indexing Can the raw, uncorrected for intensity data for InO3 be put on the site or Emailed to those who are interested? (me for starters) The profiles of the corrected data would still have to be modelled by a Variable Slit profile function but not sure what changing the intensities might be doing - even if only a minor influence on the Fundamental Parameters fit. On a slightly related topic. It would be interesting to test out these new computer controlled ADS slits vs fixed slits for Rietveld work given the old mechanical ones used to come in for criticism as being not as good as fixed slits for providing reliable intensities (and used to be far more painful to install and align compared to fixed slits). Any comments about comparison of modern computer ADS vs traditional fixed slit systems? Has the above been done? Perhaps the major problem in the past was software not completely matched to handling ADS data? I remember having an offline (verbal) discussion around two years ago where it was claimed the standard modelling/correction of ADS intensity data using the 1/(sin theta) correction as being only approximately correct. An alternative was proposed based on the fundamentals - but unfortuntely cannot remember what that was. At the time this probably helped to confirm my prejudice for fixed slit data where the physics is known with respect to intensities(?) Lachlan. -- Lachlan M. D. Cranswick Collaborative Computational Project No 14 (CCP14) for Single Crystal and Powder Diffraction Daresbury Laboratory, Warrington, WA4 4AD U.K Tel: +44-1925-603703 Fax: +44-1925-603124 E-mail: [email protected] Ext: 3703 Room C14 http://www.ccp14.ac.uk |
To: [email protected] From: Armel Le Bail [[email protected]] Mailing-List: list [email protected]; contact [email protected] Delivered-To: mailing list [email protected] Date: Tue, 06 Jun 2000 23:32:18 +0200 Reply-To: [email protected] Subject: Re: [sdpd] Reference materials for calibration and indexing >What is the average size/strain results determined on the In2O3 or >is this what the round robin will give? It is not determined. Moreover, CeO2 is part of this Round Robin, but In2O3 is not yet. The Round Robin is only at its first stage : recording patterns of selected compounds, to my knowledge. >Can the raw, uncorrected for intensity data for In2O3 >be put on the site or Emailed to those who are >interested? (me for starters) It would have been sufficient to multiply the intensities back by sin(theta). But, yes, the original uncorrected data set can be also found into PowBase now: http://sdpd.univ-lemans.fr/powbase/ Use "In2O3" as keyword (without quotes) in the search engine, the entry number is 169b. >It would be interesting to test out these new computer >controlled ADS slits vs fixed slits for Rietveld work >given the old mechanical ones used to come in for >criticism as being not as good as fixed slits for providing >reliable intensities (and used to be far more painful >to install and align compared to fixed slits). Such a comparison exists already for a NAC sample at : http://sdpd.univ-lemans.fr/powdif/low_fwhm_and_rp.html and the In2O3 data set adds a new convincing example that it works sufficiently well, with the advantage of better statistics at large angle without degrading resolution. Let me recall that WinMProf is able to treat directly the variable slit data without the need of any correction (the Rietveld approach just includes the sin(theta) term, which is less terrific than a LP correction, after all) >I remember having an offline (verbal) >discussion around two years ago where it was claimed the >standard modelling/correction of ADS intensity data using >the 1/(sin theta) correction as being only approximately >correct. This is very probably true : the correction is only approximately correct. In my experience, the error is entirely reported on the thermal parameters - which are knowingly the largest dustbin in powder diffraction analysis - so that I am not sure if the B values are degraded or improved by the process (they become slightly smaller ;-)). Best, Armel Le Bail - Universit� du Maine, Laboratoire des Fluorures, CNRS ESA 6010, Av. O. Messiaen, 72085 Le Mans Cedex 9, France http://www.cristal.org/ |
From: [email protected] Mailing-List: list [email protected]; contact [email protected] Delivered-To: mailing list [email protected] Date: Wed, 7 Jun 2000 04:40:56 +0100 (BST) Reply-To: [email protected] Subject: [sdpd] ADS and In2O3 data - XFIT Tutorial There is now a tutorial on using XFIT to profile ADS (Automatic Divergence Slit) data in Fundamental Parameters mode: http://www.ccp14.ac.uk/tutorial/xfit-95/ads_funpar.html While not shown that well in the run-through - there might be some problems as this is not fitting as well as it would with fixed slits (but some of the geometry constants may be off the optimal - plus inexperience in what to expect with ADS data) ---- A query is: how common is it for the data collection software to collect ADS data then convert it to Fixed Slit data. Would it not be better if the data is to be stored and transmitted as "fixed divergence slit" - then to generate it as fixed divergence slit data? For peak profiling (such as using Fundamental Parameters) this could cause problems if people think the data is fixed slit when it was really generated by Automatic Divergence Slits? There is at least one powder binary file format that is "lossy" with its compression algorithm. Shouldn't it be the privilege of the end user to totally abuse the data - not the programs in between? (though the tradition in Single Crystal methods is for both and more to occur?) Lachlan. -- Lachlan M. D. Cranswick Collaborative Computational Project No 14 (CCP14) for Single Crystal and Powder Diffraction Daresbury Laboratory, Warrington, WA4 4AD U.K Tel: +44-1925-603703 Fax: +44-1925-603124 E-mail: [email protected] Ext: 3703 Room C14 http://www.ccp14.ac.uk |
From: "Jens Wenzel Andreasen" [[email protected]] Mailing-List: list [email protected]; contact [email protected] Delivered-To: mailing list [email protected] Date: Wed, 7 Jun 2000 10:16:19 GMT+1 Reply-To: [email protected] Subject: Re: [sdpd] ADS and In2O3 data - XFIT Tutorial Another query which rightfully belongs in the rietveld mailing list, but bugs me a lot: Why is there so precious little software that models ADS data and none of them are any of the most well known, widely used packages such as GSAS and Fullprof? If you have ADS data and want to use any of these programs, you have to convert your data to fixed slit data. I wonder, because I imagine that it would take minimal effort to incorporate it in the software. Jens > A query is: how common is it for the data collection > software to collect ADS data then convert it to > Fixed Slit data. Would it not be better if the > data is to be stored and transmitted as "fixed > divergence slit" - then to generate it as fixed > divergence slit data? Jens Wenzel Andreasen "If only those geologists would let me Dept. of Mineralogy alone, I could do very well, but those Institute of Geology dreadful hammers! I hear the clink of University of Copenhagen them at the end of every cadece of the Phone: +45 44 64 74 10 Bible verses." - John Ruskin, 1851 |