Lachlan, while I'm sure you have every right to be excited with Koalariet,
I am not so sure that any one Rietveld program can replace all the others.
Additionally, plurality and redundance are probably a good thing.
Your description of Koalariet's ability to handle profiles is reminiscent
of a paper by W. I. F. David in JAP (I think) about internal descriptions
of profiles. XND uses them as I sure some other software out there do.
XND is written in C, the instruction file and data formats are extremely
flexible allowing the user to comment the file, and having these comments
carried through to the new files, allows arbitrary linking of parameters,
the use of different even orders of Legendre polynomials for preferred
orientation etc. etc. etc.
There ar things that XND cannot do, so I am often obliged to use GSAS and
FullProf. I am also familiar with Profil, though less so. To illustrate my
point, I mention below, things that one of these four programs can do that the
others can or cannot. Needless to say, four programs is my limit.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
XND Upside potential (to borrow stock-market jargon):
FREE !
4D space groups, very complex lineshapes, refinement of multiple
datasets acquired with some change in an external parameter such as
temperature, pressure, composition... Order-parameter like dependence of
scale factors for treating data across a phase transition, soft constraints,
very quick and stable refinements through the use of linear minimisation,
no soft limits on datasets or phases.
XND (Downside risk)
So far (I use v1.11) cannot handle TOF data, absorption corrections, magnetism
...
GSAS Upside potential
FREE !
This is a great package and most people out there are familiar with it.
Multiple datasets (X, TOF, N), quick Fourier and Patterson, ORTEP,
single-crystal refinements in the same package, magnetism, the list is
nearly endless.
Very importantly, Dr. Von Dreele as well as the large GSAS user community
are quick to help out with queries.
GSAS Downside risk
You can (though you usually don't) see the instruction file so its a bit
of a black box and mistakes are possible if you are not careful. Also,
I find that while the least squares algorithm is quick, it often blows
up when the profile is not well described and then one has to hunt for the
reason. Constant step size required within each histogram.
FullProf Upside potential
FREE !
FullProf and the programs it derives from (through DBWS to the original
Rietveld-Hewat code) is a workhorse with a large user community. It is really
convenient at the early stages of structure determination; the LeBail pattern
matching is quick and inputs are generated for SirPow and Shelx. The handling
of magnetic neutron data is unmatched. Rather comprehensive treatment of
various diffraction geometries and stuff like Pearson functions for
(STOE ??) profiles, Bessel Functions (in the new releases) to treat scattering
from rotors etc.
FullProf Downside risk
Cannot handle multiple data sets. I find the profile refinement rather painful
at times. Slower than XND. Constant step and counting time, unless you are
willing to let the program (horror!) interpolate.
Profil Upside potential
FREE !
Quick refinements on multiple data sets. The
instruction file is keyword-based (like Shelx) and very simple to use.
Jackal is like Schakal and makes great pictures of molecules.
Very nice PostScript outputs of data. Bessel functions
for disordered molecules (though I don't know how to use them!)
Profil Downside risk
Only for Unix/X (as far as I know), rather limited profiles, no magnetism.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
For myself, I thank Drs. B\'erar, Von Dreele, Rodriguez-Carvajal, Cockroft
and others for (the perhaps thankless task of) writing, documenting
and updating these programs, responding to queries, and most importantly,
for putting them on the public domain.
I hope that I have not left out important stuff and that offence has not been
caused.
I hope this convinces you Lachlan, that a single program is never sufficient.
The future may not even be Rietveld; with Maximum Entropy methods, simulated
annealing, RMC etc, there is an exciting future in powder diffration.
And finally I hope you will excuse my prolixity.
``Do I dare
Disturb the universe?
In a minute there is time
For decisions and revisions which a minute will reverse.''
Cheers
Ram
-- Dr. Ram SESHADRI (seshadri@Indigotrem1.chemie.uni-mainz.de)Anorganische Chemie, Johannes Gutenberg-UniversitaetBecher Weg 24, Mainz D55099 Germany. Phone(FAX): +49 6131 39 4417 (3922)http://Indigotrem1.chemie.uni-mainz.de/~seshadri *********************