Re: quantitative analysis - perovskites - preferred orientation

2014-02-06 Thread Leonid Solovyov
Dear Lukasz,

First of all, in the majority of Rietveld programs the uniaxial preferred 
orientation (such as [100]) can not be handled adequately for cubic systems 
since the programs normally generate only one symmetrically equivalent hkl for 
a diffraction peak. In DDM, for such cases, I included a special option 
(Expanded hkl) to generate all equivalent hkl's for every peak. This option 
makes the refinement process slower and also may require some manual settings 
for initial parameter values.
Another alternative for cubic systems is spherical harmonics.
As for the estimated error of the refined PO component, it's really wise to 
check if it exceeds the refined value, but it should be done at the final stage 
only, as at initial stages all errors may be high due to the incompleteness of 
refinement.

Best regards,
Leonid
***

Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Thursday, February 6, 2014 5:37 PM, Łukasz Kruszewski 
lkruszew...@twarda.pan.pl wrote:
 
Dear Madam/Sir(s),

I am performing Rietveld analysis for a sample containing perovskites
(CaTiO3 and SrTiO3). When putting-in a preferred orientation (PO)
correction (100 direction, as the crystals are cubic-like), I obtain
better Rwp and GOF i.e. chi-squared values (9.63 and 1.5, respectively)
than in the case of not using this correction (Rwp = 10.62 and GOF =
1.65). However, the values of the PO corrections are higher than the
errors calculated. All the other parameters including the graphical fit,
background etc., seem to be unchanged. I am also convinced about the
correctness of any input, with my diffractometer calibrated with LaB6 and
Si standards, and Beq / Uiso parameters taken directly from the CIF files
provided, so that the microabsorption factor may likely be rejected (?).
My guess is that putting in the preferred orientation might artificially,
somehow, make the fit better, maybe due to some interdependence?

Could you please kindly suggests if obtaining better statistics (Rwp, GOF)
by getting a correction values below the corresponding errors could be
treated as a good result?

Best regards!

-- 
Łukasz Kruszewski, Ph.D., adjunct
Polish Academy of Sciences
Institute of Geological Sciences
X-Ray Diffraction Laboratory (coordinator)
Twarda 51/55 str.
00-818 Warsaw
Poland
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Re: Quantitative analysis

2008-10-29 Thread Radovan Cerny

[EMAIL PROTECTED] a écrit :

Hi Blaise
 
In Bragg-Brentano mode, sample spinning does nothin for PO. This is 
because the diffraction vector is normal to the sample surface, and 
sample spinning rotates along this vector.



That's wrong! As I have already written, the empirical PO corrections 
like March-Dollase and Rietveld-Toraya suppose that the PO is fibre-like 
(axial symmetry). If your sample does not have fibre-like PO, you can 
create it by sample spinning.


Radovan

 
Spinning does increase your particle statistics, which almost always helps.
 
 
If you're looking at a capillary, spinning the capillary does help with 
PO, but just being in a capillary helps PO.
 
 
As to spinning speeds, a good guide is one revolution per data point.
 
 


Cheers

Matthew


Matthew Rowles

CSIRO Minerals
Box 312
Clayton South, Victoria
AUSTRALIA 3169

Ph: +61 3 9545 8892
Fax: +61 3 9562 8919 (site)
Email: [EMAIL PROTECTED]



--
Radovan Cerny
Laboratoire de Cristallographie
24, quai Ernest-Ansermet
CH-1211 Geneva 4, Switzerland
Phone  : [+[41] 22] 37 964 50, FAX : [+[41] 22] 37 961 08
mailto : [EMAIL PROTECTED]
URL: http://www.unige.ch/sciences/crystal/cerny/rcerny.htm




RE: Quantitative analysis

2008-10-29 Thread Daniel Chateigner
hi all,

not only fibre like, but single component fibre, and with the fibre axis
parrallel to the sample normal (i.e. cyclic fibre. this is very
restrictive and generally does not correspond to the real texture.
Contrarilly to what has been said here or there, the March-Dollase does
not ensure PO normalisation, but only the normalisation of this single
component, there is then no physical restriction between all hkl lines in
terms of crystal angles, which gives rise to a lot of fitting space with
unreasonable solutions either in terms of QTA or QPA.
A physically based correction for PO needs the calculation of the ODF, and
more than a single pattern to be measured. But this is the price to pay
for a corect estimate of phase amounts in textured samples.

daniel



-- 
Daniel Chateigner
Professeur
CRISMAT-ENSICAEN
Bd. M. Juin
14050 Caen, France
http://www.ecole.ensicaen.fr/~chateign/danielc/



Re: Quantitative analysis

2008-10-28 Thread Leonid Solovyov
Dear Mario,

One more possible problem of applying preferred orientation corrections in QPA 
is that not all of them are normalized. For example, the March-Dollase 
correction is normalized and can be applied safely, but the Rietveld-Toraya 
correction is inapplicable to QPA as it does not preserve the scale 
normalization. 

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
K. Marx av., 42
660049, Krasnoyarsk  Russia
Phone: +7 3912 495663
Fax:   +7 3912 238658
www.icct.ru/eng/content/persons/Sol_LA
***

--- On Mon, 10/27/08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:

 From: [EMAIL PROTECTED] [EMAIL PROTECTED]
 Subject: Quantitative analysis
 To: Rietveld_l@ill.fr
 Date: Monday, October 27, 2008, 3:48 PM
 Dear all,
 
 I have this question,
 
 I have been refined one mixture (of well-know percentage
 composition) of
 CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation
 in CaCO3 (104)
 and CaF2 (111) with good results. When I add to the mixture
 FeCO3 and I
 refine with preferential orientation (104), it happens that
 when I don´t
 apply the preferential orientation in all this phases, I
 have correct
 values of percentage composition, but when I apply the
 preferential
 orientation the refinement is good but with incorrect
 values of percentage
 composition. This experiment has been taken in Bragg
 Brentano geometry.
 How I should refine this mixture?
 
 Thanks a lot by your help.
 
 Mario Macías
 Universidad Industrial de Santander
 Colombia


  



RE: Quantitative analysis

2008-10-28 Thread Martin
Sorry to disagree. Experience tells me otherwise - the March-Dollase correction 
has nearly always led to poor quant results for me. It most certainly cannot be 
applied safely.
 
Martin
 
--
 
M Vickers
Dept of Chemistry
UCL



 Subject: Re: Quantitative analysis Date: Tue, 28 Oct 2008 02:53:20 -0700 
 From: [EMAIL PROTECTED] To: Rietveld_l@ill.fr  Dear Mario,  One more 
 possible problem of applying preferred orientation corrections in QPA is that 
 not all of them are normalized. For example, the March-Dollase correction is 
 normalized and can be applied safely, but the Rietveld-Toraya correction is 
 inapplicable to QPA as it does not preserve the scale normalization.   Best 
 regards, Leonid  *** 
 Leonid A. Solovyov Institute of Chemistry and Chemical Technology K. Marx 
 av., 42 660049, Krasnoyarsk Russia Phone: +7 3912 495663 Fax: +7 3912 
 238658 www.icct.ru/eng/content/persons/Sol_LA 
_
See the most popular videos on the web 
http://clk.atdmt.com/GBL/go/115454061/direct/01/

Re: Quantitative analysis

2008-10-28 Thread Radovan Cerny

Martin,

The reason of your bad experience with March-Dollase can be different, 
however, Leonid was right. The March-Dollase is normalized, the 
Rietveld-Toraya not. It can be easily normalized (see for example J. 
Appl. Cryst. 28(1995)247-253) but in all Rietveld codes I know it is not.


Best

radovan




Martin a écrit :
Sorry to disagree. Experience tells me otherwise - the March-Dollase 
correction has nearly always led to poor quant results for me. It most 
certainly cannot be applied safely.
 
Martin
 
--
 
M Vickers

Dept of Chemistry
UCL




  Subject: Re: Quantitative analysis
  Date: Tue, 28 Oct 2008 02:53:20 -0700
  From: [EMAIL PROTECTED]
  To: Rietveld_l@ill.fr
 
  Dear Mario,
 
  One more possible problem of applying preferred orientation 
corrections in QPA is that not all of them are normalized. For example, 
the March-Dollase correction is normalized and can be applied safely, 
but the Rietveld-Toraya correction is inapplicable to QPA as it does not 
preserve the scale normalization.

 
  Best regards,
  Leonid
 
  ***
  Leonid A. Solovyov
  Institute of Chemistry and Chemical Technology
  K. Marx av., 42
  660049, Krasnoyarsk Russia
  Phone: +7 3912 495663
  Fax: +7 3912 238658
  www.icct.ru/eng/content/persons/Sol_LA
 


For the best free wallpapers from MSN Click here! 
http://wallpapers.msn.com/?ocid=[B001MSN42A0716B]



--
Radovan Cerny
Laboratoire de Cristallographie
24, quai Ernest-Ansermet
CH-1211 Geneva 4, Switzerland
Phone  : [+[41] 22] 37 964 50, FAX : [+[41] 22] 37 961 08
mailto : [EMAIL PROTECTED]
URL: http://www.unige.ch/sciences/crystal/cerny/rcerny.htm




RE: Quantitative analysis

2008-10-28 Thread Omotoso, Oladipo
Mario,

You may want to check for the presence of solid solution in your siderite 
(especially Ca and Mg).  In my experience refining the PO in siderite with 
measurable amounts of Ca or Mg correlates significantly with the occupancy if 
the Fe/(Ca or Mg) ratio is not constrained to the true chemistry. The chemistry 
may be estimated by the d104 shift.

Dipo Omotoso
Natural Resources Canada
CETC-Devon
#1 Oil Patch drive, Devon AB. T9G 1A8.



-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Mon 10/27/2008 7:10 PM
To: [EMAIL PROTECTED]; Rietveld_l@ill.fr
Subject: RE: Quantitative analysis
 
Dear Mario,

Please tell me a little about the data collection conditions you used for this 
work:-

How was the sample prepared (hand ground, micronised in McCrone mill )
What was the tube target Cu, Co, other ??

Cheers
Ian Madsen

From: [EMAIL PROTECTED] [EMAIL PROTECTED]
Sent: Tuesday, October 28, 2008 2:48 AM
To: Rietveld_l@ill.fr
Subject: Quantitative analysis

Dear all,

I have this question,

I have been refined one mixture (of well-know percentage composition) of
CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation in CaCO3 (104)
and CaF2 (111) with good results. When I add to the mixture FeCO3 and I
refine with preferential orientation (104), it happens that when I don´t
apply the preferential orientation in all this phases, I have correct
values of percentage composition, but when I apply the preferential
orientation the refinement is good but with incorrect values of percentage
composition. This experiment has been taken in Bragg Brentano geometry.
How I should refine this mixture?

Thanks a lot by your help.

Mario Macías
Universidad Industrial de Santander
Colombia





RE: Quantitative analysis

2008-10-28 Thread Whitfield, Pamela
While my coffee pot gurgles away here's my tuppence worth

As mentioned by previous answers prevention is MUCH better than cure.

Having said that a couple of comments.  If there's significant PO then it's a 
pretty sure thing that the particles are not spherical - so you can forget the 
Brindley correction which assumes spherical (and also monodisperse BTW) 
particles.  PO is also strongly suggestive (but not certain) of fairly large 
particles, so microabsorption could be pretty severe. In this case with FeCO3 
and Cu radiation microabsorption is going to be an issue independent of whether 
the PO correction preserves the scale normalization.

Pam


Dr Pamela Whitfield MRSC CChem
Energy Materials
Institute for Chemical Process and Environmental Technology (ICPET)
Building M12
National Research Council Canada
1200 Montreal Road
Ottawa  ON  K1A 0R6
CANADA

Tel: (613) 998-8462Fax: (613) 991 2384
Email: [EMAIL PROTECTED]



-Original Message-
From: Leonid Solovyov [mailto:[EMAIL PROTECTED] 
Sent: October 28, 2008 5:53 AM
To: Rietveld_l@ill.fr
Subject: Re: Quantitative analysis

Dear Mario,

One more possible problem of applying preferred orientation corrections in QPA 
is that not all of them are normalized. For example, the March-Dollase 
correction is normalized and can be applied safely, but the Rietveld-Toraya 
correction is inapplicable to QPA as it does not preserve the scale 
normalization. 

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
K. Marx av., 42
660049, Krasnoyarsk  Russia
Phone: +7 3912 495663
Fax:   +7 3912 238658
www.icct.ru/eng/content/persons/Sol_LA
***

--- On Mon, 10/27/08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:

 From: [EMAIL PROTECTED] [EMAIL PROTECTED]
 Subject: Quantitative analysis
 To: Rietveld_l@ill.fr
 Date: Monday, October 27, 2008, 3:48 PM
 Dear all,
 
 I have this question,
 
 I have been refined one mixture (of well-know percentage
 composition) of
 CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation
 in CaCO3 (104)
 and CaF2 (111) with good results. When I add to the mixture
 FeCO3 and I
 refine with preferential orientation (104), it happens that
 when I don´t
 apply the preferential orientation in all this phases, I
 have correct
 values of percentage composition, but when I apply the
 preferential
 orientation the refinement is good but with incorrect
 values of percentage
 composition. This experiment has been taken in Bragg
 Brentano geometry.
 How I should refine this mixture?
 
 Thanks a lot by your help.
 
 Mario Macías
 Universidad Industrial de Santander
 Colombia


  




RE: Quantitative analysis

2008-10-28 Thread David L. Bish
I agree that it's always best to avoid preferred orientation, but that is 
easier said than done on a routine basis.  I have personally had good luck 
with the M-D PO correction on many known samples, as long as the PO was not 
severe.


However, I imagine that Mario's problems are related to microabsorption in 
this case.  Mario, if you can re-measure your data with a Co or Fe tube, it 
would be a good test of this.


Dave Bish

At 08:51 AM 10/28/2008 -0400, Martin wrote:
Sorry to disagree. Experience tells me otherwise - the March-Dollase 
correction has nearly always led to poor quant results for me. It most 
certainly cannot be applied safely.


Martin

--

M Vickers
Dept of Chemistry
UCL



--

 Subject: Re: Quantitative analysis
 Date: Tue, 28 Oct 2008 02:53:20 -0700
 From: [EMAIL PROTECTED]
 To: Rietveld_l@ill.fr

 Dear Mario,

 One more possible problem of applying preferred orientation corrections 
in QPA is that not all of them are normalized. For example, the 
March-Dollase correction is normalized and can be applied safely, but the 
Rietveld-Toraya correction is inapplicable to QPA as it does not preserve 
the scale normalization.


 Best regards,
 Leonid

 ***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 K. Marx av., 42
 660049, Krasnoyarsk Russia
 Phone: +7 3912 495663
 Fax: +7 3912 238658
 www.icct.ru/eng/content/persons/Sol_LA



--
For the best free wallpapers from MSN Click here!


RE: Quantitative analysis

2008-10-28 Thread mariomacias
Dear all,

the well-known data are: CaCO3 (20%), CaF2 (35%), SiO2 (1%), Al2O3 (20%),
and FeCO3 (24%). The data obtained without PO are: CaCO3 (24%), CaF2
(36%), SiO2 (1%), Al2O3 (17%), and FeCO3 (23%). The data obtained with PO
are: CaCO3 (19%), CaF2 (32%), SiO2 (2%), Al2O3 (31%), and FeCO3 (16%).
it seems to have a problem among Al2O3 and FeCO3 data after PO.

Mario.


 Dear all,

 The data collection conditions is: hand grind (35 microns), scan:
 2Theta/Theta Coupled, to steps 2 sec., target Cu, graphite monochromator,
 side loading. The correction of preferential orientation has been refined
 by March-Dollase model.

 Thanks a lot,

 Mario.




 Dear Mario,

 Please tell me a little about the data collection conditions you used
 for
 this work:-

 How was the sample prepared (hand ground, micronised in McCrone mill
 )
 What was the tube target Cu, Co, other ??

 Cheers
 Ian Madsen
 
 From: [EMAIL PROTECTED] [EMAIL PROTECTED]
 Sent: Tuesday, October 28, 2008 2:48 AM
 To: Rietveld_l@ill.fr
 Subject: Quantitative analysis

 Dear all,

 I have this question,

 I have been refined one mixture (of well-know percentage composition) of
 CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation in CaCO3
 (104)
 and CaF2 (111) with good results. When I add to the mixture FeCO3 and I
 refine with preferential orientation (104), it happens that when I don´t
 apply the preferential orientation in all this phases, I have correct
 values of percentage composition, but when I apply the preferential
 orientation the refinement is good but with incorrect values of
 percentage
 composition. This experiment has been taken in Bragg Brentano geometry.
 How I should refine this mixture?

 Thanks a lot by your help.

 Mario Macías
 Universidad Industrial de Santander
 Colombia











RE: Quantitative analysis

2008-10-28 Thread Mibeck, Blaise
 

I am learning QPA and am worried about PO. 

 

I wonder why sample spinning isn't discussed more. 

 

I am luckily able to barrow time on a newer diffractometer with a sample
spinner. 

 

Does this reduce PO? Or completely eliminate it? There is a set up
variable in GSAS for whether you are spinning the sample - are there
guidelines for how many revolutions to spin the sample if you just want
to reduce PO?

 

Thanks to all for there help!!!

Blaise

 

 

 

 

* * * * * * * * * * * * * 

Blaise Mibeck 

Research Scientist

Energy  Environmental Research Center

University of North Dakota

15 North 23rd Street, Stop 9018

Grand Forks, ND 58202-9018

 

Phone: (701) 777-5077

Email: [EMAIL PROTECTED]

 

 

-Original Message-
From: David L. Bish [mailto:[EMAIL PROTECTED] 
Sent: Tuesday, October 28, 2008 9:09 AM
To: Martin; [EMAIL PROTECTED]; rietveld_l@ill.fr
Subject: RE: Quantitative analysis

 

I agree that it's always best to avoid preferred orientation, but that
is easier said than done on a routine basis.  I have personally had good
luck with the M-D PO correction on many known samples, as long as the PO
was not severe.

However, I imagine that Mario's problems are related to microabsorption
in this case.  Mario, if you can re-measure your data with a Co or Fe
tube, it would be a good test of this.

Dave Bish

At 08:51 AM 10/28/2008 -0400, Martin wrote:



Sorry to disagree. Experience tells me otherwise - the March-Dollase
correction has nearly always led to poor quant results for me. It most
certainly cannot be applied safely.
 
Martin
 
--
 
M Vickers
Dept of Chemistry
UCL






 Subject: Re: Quantitative analysis
 Date: Tue, 28 Oct 2008 02:53:20 -0700
 From: [EMAIL PROTECTED]
 To: Rietveld_l@ill.fr
 
 Dear Mario,
 
 One more possible problem of applying preferred orientation
corrections in QPA is that not all of them are normalized. For example,
the March-Dollase correction is normalized and can be applied safely,
but the Rietveld-Toraya correction is inapplicable to QPA as it does not
preserve the scale normalization. 
 
 Best regards,
 Leonid
 
 ***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 K. Marx av., 42
 660049, Krasnoyarsk Russia
 Phone: +7 3912 495663
 Fax: +7 3912 238658
 www.icct.ru/eng/content/persons/Sol_LA
 



For the best free wallpapers from MSN Click here!
http://wallpapers.msn.com/?ocid  



Re: Quantitative analysis

2008-10-28 Thread Radovan Cerny
The empirical PO corrections like March-Dollase or Rietveld-Toraya can 
correct only for fibre like PO, i.e. symmetrical around one axis. If it 
is not your case, you can make it fibre like by spinning, if you spin 
around the PO vector. If not than see J. Appl. Cryst. 28(1995)247-253.


However, there are few other limitations, which are usually completly 
ignored:


The distribution of crystallites around any pole hkl must be axially 
symmetrical either, so-called disc- or rod-shape like behavior. No way 
to do it by spinning ...


Most of implementations of these corrections in the Rietveld codes also 
assume another condition: The texture axis is parallel (or 
perpendicular) to the diffraction vector for all measured hkls. This 
condition is fullfilled only in Bragg-Brentano or Debye-Scherrer geometries.


Surprising that it still works ...


Radovan


Mibeck, Blaise a écrit :
 


I am learning QPA and am worried about PO.

 


I wonder why sample spinning isn’t discussed more.

 

I am luckily able to barrow time on a newer diffractometer with a sample 
spinner.


 

Does this reduce PO? Or completely eliminate it? There is a set up 
variable in GSAS for whether you are spinning the sample – are there 
guidelines for how many revolutions to spin the sample if you just want 
to reduce PO?


 


Thanks to all for there help!!!

Blaise

 

 

 

 


* * * * * * * * * * * * *

Blaise Mibeck

Research Scientist

Energy  Environmental Research Center

University of North Dakota

15 North 23rd Street, Stop 9018

Grand Forks, ND 58202-9018

 


Phone: (701) 777-5077

Email: [EMAIL PROTECTED] mailto:[EMAIL PROTECTED]

 

 


-Original Message-
*From:* David L. Bish [mailto:[EMAIL PROTECTED]
*Sent:* Tuesday, October 28, 2008 9:09 AM
*To:* Martin; [EMAIL PROTECTED]; rietveld_l@ill.fr
*Subject:* RE: Quantitative analysis

 

I agree that it's always best to avoid preferred orientation, but that 
is easier said than done on a routine basis.  I have personally had good 
luck with the M-D PO correction on many known samples, as long as the PO 
was not severe.


However, I imagine that Mario's problems are related to microabsorption 
in this case.  Mario, if you can re-measure your data with a Co or Fe 
tube, it would be a good test of this.


Dave Bish

At 08:51 AM 10/28/2008 -0400, Martin wrote:

Sorry to disagree. Experience tells me otherwise - the March-Dollase 
correction has nearly always led to poor quant results for me. It most 
certainly cannot be applied safely.
 
Martin
 
--
 
M Vickers

Dept of Chemistry
UCL





 Subject: Re: Quantitative analysis
 Date: Tue, 28 Oct 2008 02:53:20 -0700
 From: [EMAIL PROTECTED]
 To: Rietveld_l@ill.fr

 Dear Mario,

 One more possible problem of applying preferred orientation 
corrections in QPA is that not all of them are normalized. For example, 
the March-Dollase correction is normalized and can be applied safely, 
but the Rietveld-Toraya correction is inapplicable to QPA as it does not 
preserve the scale normalization.


 Best regards,
 Leonid

 ***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 K. Marx av., 42
 660049, Krasnoyarsk Russia
 Phone: +7 3912 495663
 Fax: +7 3912 238658
 www.icct.ru/eng/content/persons/Sol_LA 

http://www.icct.ru/eng/content/persons/Sol_LA






For the best free wallpapers from MSN Click here! 
http://wallpapers.msn.com/?ocid





--
Radovan Cerny
Laboratoire de Cristallographie
24, quai Ernest-Ansermet
CH-1211 Geneva 4, Switzerland
Phone  : [+[41] 22] 37 964 50, FAX : [+[41] 22] 37 961 08
mailto : [EMAIL PROTECTED]
URL: http://www.unige.ch/sciences/crystal/cerny/rcerny.htm




RE: Quantitative analysis

2008-10-28 Thread Omotoso, Oladipo
Mario,

From the information that you just gave, it appears that the corundum 012 and 
siderite 012 are not well resolved causing more of the siderite 012 intensity 
to be attributed to the corundum 012 and an overestimation of corundum.  If it 
is a microabsorption problem, you wouldn't get a good QPA data without PO 
correction to start with. If you can, reduce the receiving slit size and run 
the sample again or don't correct for PO.

Dipo Omotoso   

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 
Sent: October 28, 2008 8:24 AM
To: Rietveld_l@ill.fr
Subject: RE: Quantitative analysis

Dear all,

the well-known data are: CaCO3 (20%), CaF2 (35%), SiO2 (1%), Al2O3 (20%), and 
FeCO3 (24%). The data obtained without PO are: CaCO3 (24%), CaF2 (36%), SiO2 
(1%), Al2O3 (17%), and FeCO3 (23%). The data obtained with PO
are: CaCO3 (19%), CaF2 (32%), SiO2 (2%), Al2O3 (31%), and FeCO3 (16%).
it seems to have a problem among Al2O3 and FeCO3 data after PO.

Mario.


 Dear all,

 The data collection conditions is: hand grind (35 microns), scan:
 2Theta/Theta Coupled, to steps 2 sec., target Cu, graphite 
 monochromator, side loading. The correction of preferential 
 orientation has been refined by March-Dollase model.

 Thanks a lot,

 Mario.




 Dear Mario,

 Please tell me a little about the data collection conditions you used 
 for this work:-

 How was the sample prepared (hand ground, micronised in McCrone mill
 )
 What was the tube target Cu, Co, other ??

 Cheers
 Ian Madsen
 
 From: [EMAIL PROTECTED] [EMAIL PROTECTED]
 Sent: Tuesday, October 28, 2008 2:48 AM
 To: Rietveld_l@ill.fr
 Subject: Quantitative analysis

 Dear all,

 I have this question,

 I have been refined one mixture (of well-know percentage composition) 
 of CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation in 
 CaCO3
 (104)
 and CaF2 (111) with good results. When I add to the mixture FeCO3 and 
 I refine with preferential orientation (104), it happens that when I 
 don´t apply the preferential orientation in all this phases, I have 
 correct values of percentage composition, but when I apply the 
 preferential orientation the refinement is good but with incorrect 
 values of percentage composition. This experiment has been taken in 
 Bragg Brentano geometry.
 How I should refine this mixture?

 Thanks a lot by your help.

 Mario Macías
 Universidad Industrial de Santander
 Colombia












RE: Quantitative analysis

2008-10-28 Thread mariomacias
Thank you to all for your generous help... has been very important your
information..

Mario.



Mario,

 From the information that you just gave, it appears that the corundum 012
 and siderite 012 are not well resolved causing more of the siderite 012
 intensity to be attributed to the corundum 012 and an overestimation of
 corundum.  If it is a microabsorption problem, you wouldn't get a good QPA
 data without PO correction to start with. If you can, reduce the receiving
 slit size and run the sample again or don't correct for PO.

 Dipo Omotoso

 -Original Message-
 From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
 Sent: October 28, 2008 8:24 AM
 To: Rietveld_l@ill.fr
 Subject: RE: Quantitative analysis

Dear all,

 the well-known data are: CaCO3 (20%), CaF2 (35%), SiO2 (1%), Al2O3 (20%),
 and FeCO3 (24%). The data obtained without PO are: CaCO3 (24%), CaF2
 (36%), SiO2 (1%), Al2O3 (17%), and FeCO3 (23%). The data obtained with PO
 are: CaCO3 (19%), CaF2 (32%), SiO2 (2%), Al2O3 (31%), and FeCO3 (16%).
 it seems to have a problem among Al2O3 and FeCO3 data after PO.

 Mario.


  Dear all,

 The data collection conditions is: hand grind (35 microns), scan:
 2Theta/Theta Coupled, to steps 2 sec., target Cu, graphite
 monochromator, side loading. The correction of preferential
 orientation has been refined by March-Dollase model.

 Thanks a lot,

 Mario.




 Dear Mario,

 Please tell me a little about the data collection conditions you used
 for this work:-

 How was the sample prepared (hand ground, micronised in McCrone mill
 )
 What was the tube target Cu, Co, other ??

 Cheers
 Ian Madsen
 
 From: [EMAIL PROTECTED] [EMAIL PROTECTED]
 Sent: Tuesday, October 28, 2008 2:48 AM
 To: Rietveld_l@ill.fr
 Subject: Quantitative analysis

 Dear all,

 I have this question,

 I have been refined one mixture (of well-know percentage composition)
 of CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation in
 CaCO3
 (104)
 and CaF2 (111) with good results. When I add to the mixture FeCO3 and
 I refine with preferential orientation (104), it happens that when I
 don´t apply the preferential orientation in all this phases, I have
 correct values of percentage composition, but when I apply the
 preferential orientation the refinement is good but with incorrect
 values of percentage composition. This experiment has been taken in
 Bragg Brentano geometry.
 How I should refine this mixture?

 Thanks a lot by your help.

 Mario Macías
 Universidad Industrial de Santander
 Colombia
















RE: Quantitative analysis

2008-10-28 Thread Martin
Spinning the sample doesn't reduce preferred orientation much. It does, 
however, improve ones counting statistics very nicely.
 
Martin 
 

M Vickers
Dept. of Chemistry
UCL
20, Gordon Street
London
WC1E 0HX



Subject: RE: Quantitative analysisDate: Tue, 28 Oct 2008 09:25:13 -0500From: 
[EMAIL PROTECTED]: rietveld_l@ill.fr




 
I am learning QPA and am worried about PO. 
 
I wonder why sample spinning isn’t discussed more. 
 
I am luckily able to barrow time on a newer diffractometer with a sample 
spinner. 
 
Does this reduce PO? Or completely eliminate it? There is a set up variable in 
GSAS for whether you are spinning the sample – are there guidelines for how 
many revolutions to spin the sample if you just want to reduce PO?
 
Thanks to all for there help!!!
Blaise
 
 
 
 

* * * * * * * * * * * * * 
Blaise Mibeck 
Research Scientist
Energy  Environmental Research Center
University of North Dakota
15 North 23rd Street, Stop 9018
Grand Forks, ND 58202-9018
 
Phone: (701) 777-5077
Email: [EMAIL PROTECTED]
_
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RE: Quantitative analysis

2008-10-28 Thread Matthew.Rowles
Hi Blaise

In Bragg-Brentano mode, sample spinning does nothin for PO. This is because the 
diffraction vector is normal to the sample surface, and sample spinning rotates 
along this vector.

Spinning does increase your particle statistics, which almost always helps.


If you're looking at a capillary, spinning the capillary does help with PO, but 
just being in a capillary helps PO.


As to spinning speeds, a good guide is one revolution per data point.




Cheers

Matthew


Matthew Rowles

CSIRO Minerals
Box 312
Clayton South, Victoria
AUSTRALIA 3169

Ph: +61 3 9545 8892
Fax: +61 3 9562 8919 (site)
Email: [EMAIL PROTECTED]




From: Mibeck, Blaise [mailto:[EMAIL PROTECTED]
Sent: Wednesday, 29 October 2008 01:25
To: rietveld_l@ill.fr
Subject: RE: Quantitative analysis


I am learning QPA and am worried about PO.

I wonder why sample spinning isn't discussed more.

I am luckily able to barrow time on a newer diffractometer with a sample 
spinner.

Does this reduce PO? Or completely eliminate it? There is a set up variable in 
GSAS for whether you are spinning the sample - are there guidelines for how 
many revolutions to spin the sample if you just want to reduce PO?

Thanks to all for there help!!!
Blaise




* * * * * * * * * * * * *
Blaise Mibeck
Research Scientist
Energy  Environmental Research Center
University of North Dakota
15 North 23rd Street, Stop 9018
Grand Forks, ND 58202-9018

Phone: (701) 777-5077
Email: [EMAIL PROTECTED]mailto:[EMAIL PROTECTED]


-Original Message-
From: David L. Bish [mailto:[EMAIL PROTECTED]
Sent: Tuesday, October 28, 2008 9:09 AM
To: Martin; [EMAIL PROTECTED]; rietveld_l@ill.fr
Subject: RE: Quantitative analysis

I agree that it's always best to avoid preferred orientation, but that is 
easier said than done on a routine basis.  I have personally had good luck with 
the M-D PO correction on many known samples, as long as the PO was not severe.

However, I imagine that Mario's problems are related to microabsorption in this 
case.  Mario, if you can re-measure your data with a Co or Fe tube, it would be 
a good test of this.

Dave Bish

At 08:51 AM 10/28/2008 -0400, Martin wrote:

Sorry to disagree. Experience tells me otherwise - the March-Dollase correction 
has nearly always led to poor quant results for me. It most certainly cannot be 
applied safely.

Martin

--

M Vickers
Dept of Chemistry
UCL



 Subject: Re: Quantitative analysis
 Date: Tue, 28 Oct 2008 02:53:20 -0700
 From: [EMAIL PROTECTED]
 To: Rietveld_l@ill.fr

 Dear Mario,

 One more possible problem of applying preferred orientation corrections in 
 QPA is that not all of them are normalized. For example, the March-Dollase 
 correction is normalized and can be applied safely, but the Rietveld-Toraya 
 correction is inapplicable to QPA as it does not preserve the scale 
 normalization.

 Best regards,
 Leonid

 ***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 K. Marx av., 42
 660049, Krasnoyarsk Russia
 Phone: +7 3912 495663
 Fax: +7 3912 238658
 www.icct.ru/eng/content/persons/Sol_LAhttp://www.icct.ru/eng/content/persons/Sol_LA


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here!http://wallpapers.msn.com/?ocid


RE: Quantitative analysis

2008-10-27 Thread Kurt Leinenweber
Dear Mario,

If the quantity of FeCO3 appears to be smaller than the actual value, then it 
could be due to absorption.  If you are using a copper source (CuKalpha) then 
that excites iron fluorescence, which is radiated equally in all directions... 
this means that the beam does not penetrate the FeCO3 particles entirely, and 
results in incomplete diffraction from these particles.

There are programs that correct for this problem, but as far as I know there is 
no freeware to deal with this effect.

- Kurt

 
*
Kurt Leinenweber
Dept. of Chemistry and Biochemistry
Arizona State University
Tempe, AZ 85287-1604
 
phone (480)-965-8853
fax (480)-965-2747
 
***

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 
Sent: Monday, October 27, 2008 8:48 AM
To: Rietveld_l@ill.fr
Subject: Quantitative analysis

Dear all,

I have this question,

I have been refined one mixture (of well-know percentage composition) of
CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation in CaCO3 (104)
and CaF2 (111) with good results. When I add to the mixture FeCO3 and I
refine with preferential orientation (104), it happens that when I don´t
apply the preferential orientation in all this phases, I have correct
values of percentage composition, but when I apply the preferential
orientation the refinement is good but with incorrect values of percentage
composition. This experiment has been taken in Bragg Brentano geometry.
How I should refine this mixture?

Thanks a lot by your help.

Mario Macías
Universidad Industrial de Santander
Colombia






RE: Quantitative analysis

2008-10-27 Thread Martin
Dear Mario, My experience of quant Rietveld is much the same as yours - poor 
quant result if using any sort of PO function. Advise as others have here - 
reduce PO. Capillary geometry may help in many instances but in this case could 
then have problems with absorption seeing as you will most likely be having to 
use Co radiation to avoid fluorescence from the iron. Good luck, Martin
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