Dear all,
so we are having a philosophical discussion - after being distracted all
day it is evening, my users seem happy and I have some time to add my 5c
worth to the discussion. For those who do not know me, I am running NPDF
at the Lujan Center and we aim to bring PDF (neutron PDF) to the worl
Dear all,
> Let's see if this gets through. I recently moved to APS & my "official"
> e-mail address changed but not my "public" one ([EMAIL PROTECTED]).
> OK, my comments on PDF vs/and Rietveld refinement.
...
> I fully agree with Alan's definition of "Rietveld Refinement"; I usually
> describe
Pam and all,
I too have been looking at materials using in house lab data. Using an
Ag rotating anode (I actually used Ag-k beta for simplicity of the lack
of peak splitting) and an MSC curved imaging plate, and very long
exposures we got data we found quite useful. However, I stopped playing
in
Let's see if this gets through. I recently moved to APS & my "official"
e-mail address changed but not my "public" one ([EMAIL PROTECTED]).
OK, my comments on PDF vs/and Rietveld refinement.
First both techniques use the same raw data; one directly & the other
after a lot of corrections (some pe
To continue ...
On 13 Jun 2008, at 14:37, Alan Hewat wrote:
Martin gives a good example for which interesting new information was
obtained from the PDF function - the fact that the Si-O bond lengths
do
not change during a structural transition in quartz.
But quartz is a rather special case.
Martin gives a good example for which interesting new information was
obtained from the PDF function - the fact that the Si-O bond lengths do
not change during a structural transition in quartz.
But quartz is a rather special case. First of all quartz is simple enough
that the Si-O distances might
I'm only going to stick my big toe in here on a practical note for
lab-based studies.
I managed to get the Bruker Vantec detector to work with MoKa quite
nicely for some non-ambient work and decided to see if I could get
useful data for PDF from some battery cathode materials (I think it was
up to
just my two cents.. even if I'm aware that times are not yet mature for a
comparison of this type.
There is lot of enthusiasm behind the use of the PDF approach and the
number of symposia in conferences, as well as the number of talks on the
subject is increasing day after day... the true ques
Dear all
I have to weigh in here as someone who has been using total scattering
measurements for some while now.
I suggest that since this is a crystallography mail list I should
restrict discussion to crystals and not amorphous or nano-crystalline
materials.
What Bragg diffraction give
Hi Alan
I wrote a reply to the discussion about PDF that I hoped made a useful
contribution, but then realised that with system changes my registered
email address on the list is not the same as my sending email address.
I have applied for a new membership and will then remove the old one,
Thanks all for the PDF explanations
I think I'm beginning to understand. To summarise what we know:
- PDF for powder data is a Patterson function (as Alan Hewat stated) in one
dimension that plots the histogram of atom separation
- It will show quite nicely the short range order and then possibl
Sorry, this got bounced last night so I am resending.
-- Forwarded message --
From: Simon Billinge <[EMAIL PROTECTED]>
Date: Thu, Jun 12, 2008 at 9:30 PM
Subject: Fwd: PDF refinement pros and cons
To: rietveld_l@ill.fr
Hi Alan, greetings to the Antipodes.
Fitting F(Q) and G(r) s
Hi,
I've only begun to look at pdf, but it seems to me that pdf is only really
interesting if you want to model non-crystalline material (or
nano-crystalline), so that there is no long-range periodicity (limited size,
defects on the borders, large strain, variation in composition,...)
Oh good ! We are going to have one of those philosophical debates about
the fundamentals of Rietveld related refinement, where we can all safely
defend different opinions based on our limited personal experience.
PDF refinement is great, but is not new. It was known as the "Patterson
function" in
Alan
I think you are misunderstanding what the PDF method is used for. The
idea is to fourier transform directly the whole range of scattering
including peaks and background (after removing artifacts in the
background due to the diffractometer, air scattering etc). In a highly
ordered crystal stru
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