> > Is there a program which can take as input the atomic positions and
> > lattice parameters and the associated errors and give as an output an
> > estimation of the bond lengths, angles and associated errors? I think
> > that doing this would give an overestimation of the errors (for example it
> > neglects any correlation in atomic positions) even if such a program
> > exists.
>
> This may be a pedantic point, but standard uncertainties (aka esd's)
> really should be estimated using the covariance matrix. If you estimate
> uncertainties without using the correlation information in the matrix,
> your results can be significantly higher or lower (or unchanged)
> depending from the best estimates, depending on the sign and magnitude
> of the correlation coefficients.
>
> It has been a couple of decades now, but I seem to recall modifying
> ORFEE for exactly this purpose -- reading atomic parameters and the
> covariance matrix from a refinement program to get distances and angles
> with S.U. I suspect Larry Finger's program BONDAN and many others could
> be adapted as well.
Another available program for bond-length/angle calculation with
ESDs is:
Sadian 91. Reference:
W.H. Baur and D. Kassner: Sadian90 prepares input for DLS-76 (and does
other things as well. Z. Krist. Suppl. Issue, No. 3, 15 (1991))
ftp://ftp.minerals.csiro.au/pub/xtallography/sadian91/
http://www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/csirominerals-anon-ftp/pub/xtallography/sadian91/
-------
If you can get the data into a Shelx, CIF or Platon SPF format,
this gives the option of using Platon. Platon, like Shelx gives
the bond-length/angle output in a polyhedral format which can
be very easy to interpret. You could do the same with Shelx
by giving Shelx a "dummy" HKL file. Though this can be more
tedious.
This would not generate errors though but could give a quick
quality check for following the structure.
There is a turorial run-through of interactively/graphically
checking bond-lengths angles with Platon at:
http://www.ccp14.ac.uk/tutorial/platon/atomenv.htm
----
Another option is to import the file into GUI WinORTEP
which can read GSAS, Fullprof, LHPM/Rietica files as well
as the usual Single crystal and CIF file formats.
http://www.chem.gla.ac.uk/~louis/ortep3/
http://www.ccp14.ac.uk/ccp/web-mirrors/farrugia/~louis/ortep3/
---
Repeating a comment made before(?), that if people involved with
hacking into Rietveld kernels output a few common formats
such as Shelx and CIF, this can then transparently link into
other structure viewing and checking software (even Fourier
map generation and viewing), enhancing the possible quality
of analysis with little effort - and freeing up programming
time for concentrating on adding functionality to
the Rietveld kernel.
Lachlan.
--
Lachlan M. D. Cranswick
Collaborative Computational Project No 14 (CCP14)
for Single Crystal and Powder Diffraction
Daresbury Laboratory, Warrington, WA4 4AD U.K
Tel: +44-1925-603703 Fax: +44-1925-603124
E-mail: [EMAIL PROTECTED] Ext: 3703 Room C14
http://www.ccp14.ac.uk
