{{{ SNIP, SNIP, SNIP }}}
>I remember after giving a talk at a Rietveld workshop (on the
>lines of what "would it be like if you tried to do quantitative
>Rietveld analysis" - on the Rutile/Ilmenite phase system)
>there were some personal comments bemoaning that it was a pity
>there are not more "Rietveld Failures" or
>"I Tried to do Rietveld Analysis and it Ruined my Life" type
>of review articles in the literature. Or perhaps just balanced
>reviews. (The above didn't ruin my life entirely as shown by
>results published in:
>
> R. R. Merritt and L. M. D. Cranswick, Proceedings of the
> 6th AusIMM Extractive Metallurgy Conference, Brisbane,
> 3-6 July, 1994, pp 171-180)
>
>Reading much of the literature on Rietveld analysis can give
>an unrealistic picture on how easy it is to perform.
>Whereas in reality it can be quite tricky, problematic, frustrating
>and very easy to get wrong results without realizing it
>if you don't keep your wits about you.
>
{{{ SNIP, SNIP, SNIP }}}
I'd like to share an initial experience I had with learning Rietveld, which
still causes a nightmare or two - there are some who think it suitable for
novices to use routinely. When I came to the University two years ago, I
was forced to go through an INTRODUCTORY Xray class before I could have my
dosimeters, although I had an MS in Engineering (thermo), an MS in chemistry
(molecular spectroscopy/crystallography), 6 years single crystal experience,
and 2 years powder. My introduction to Rietveld came, in this class, from
someone who was of the opinion that to perform quantitative Rietveld
Analysis, all one needed to do was enter the single crystal info and refine
scale factors for phase abundances, and phase ID is based on the major peaks
in the pattern, with minors ignored if they don't quite fit.
I was very fortunate, compared to the rest of the class who had no X-ray
background at all, so didn't die when the class project - take a mineral
sample, grind it to powder, X-ray it, identify all phases and perform a full
Rietveld analysis of the data, with no background or theory on the
technique, yet, just the program and a manual - was assigned the last two
weeks of class - I only came close }:^) ... I'm the only one doing my own
analyses, unassisted, to this day ...
{{{SNIP}}}
>Phase Identification can be of similar frustration if you
>are not informed of the pitfalls in advance.
>
>It would be nice if there was a web or internet database people
>could submit problems that occurred - and their solutions. Though I
>expect time constraints and people being a bit shy on revealing
>the problems they had might make this suggestion somewhat of a
>fantasy. "Failure databases" could be one of the interesting
>applications of the internet for science and education.
>Though most likely they would eventually become failure and
>solution databases(?).
{{{SNIP}}}
One might hope - it would be wonderful for teaching purposes.
{{{SNIP}}}
Linda D. Mansker EMAIL: mansker@unm.edu
Chemical and Nuclear Engineering (505) 277-5841
University of New Mexico FAX: (505) 277-5433
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"Out of clutter, find simplicity. From discord, find harmony.
In the middle of difficulty, lies opportunity."
Albert Einstein
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