Dear Lubomir Smrock,
linear pattern analysis is _not_ Rietveld, this was a common QPA
method prior to Rietveld QPA. In a Rietvel QPA, one must refine
the lattice parameter at least. And that makes it nonlinear.
Depending on the sample, one may decide to add more nonlinear
details to the
Dear colleagues,
sorry, my mail should go directly to Leandro, but I used this damned
reply buttom...
My answer was related to Leandro's questions regarding these line
broadening models. I realised that Leandro is going on to apply a
Rietveld program for phase quantification, including
Clay people
I think the single crystal analysis of clays is interesting. I have not read
the literature but in determining the intensities is overlap of the dots
considered as I would have expected the dots to be very much smeared (5 to
10 degrees 2Th in my experience). If yes the fitting in two
I have to disagree with that; at least on a practical front with lab XRD. I
have done measurements myself with samples containing large portlandite plates
(granted, not a silicate but lovely-looking plates in a SEM) for quantitative
analysis. The whole point of the work was to see if
Lubo
SVD as you mentioned does avoid numerical problems as does other methods
such as the conjugate gradient method. SVD minimizes on the residuals |A x -
b| after solving the matrix equation A x = b.
I would like to point out however that errors obtained from the covariance
matrix are an
My limited experience with X-ray capillary measurements of ultra fine clay
minerals suggests that you could have significant preferred orientation along
the b* axis. It is actually a good way of determining aspect ratios in
phyllosilicates.
Dipo Omotoso
Makes sense with ultra-fines. My portlandite grains were 5 microns upwards.
I'm working to avoid ultra-fines even harder than the bigger stuff :-)
Pam
From: Omotoso, Oladipo [mailto:[EMAIL PROTECTED]
Sent: Wed 21/03/2007 10:47 AM
To: rietveld_l@ill.fr
Subject:
