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 include
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 P
[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
li
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 s
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
ipo 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
: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
in; [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
n 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 02:5
>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%).
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
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 cor
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
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
> 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
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: Quantitat
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
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 like
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 PROTECTE
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
Dear Mario,
I only use PO to check if it applies. If yes, I make a new preparation to avoid
PO. Also, graininess may look similar to PO, and this would surely bias QPA
if PO refinement is allowed for.
So my advice is: grind, grind, grind.
Best
miguel
On 27 Oct 2008 at 10:48, [EMAIL PROTECTE
21 matches
Mail list logo
