[Ifeffit] Problem reproducing spectrum for Ti complex

Bruce Ravel bravel at bnl.gov
Fri Aug 29 17:05:30 CDT 2008


I don't have a lot of advice, but there are a few more things to try.
The RSIGMA keyword completely removes the broadening -- that's clearly
no correct, but I think it will give you a sense of how the spectrum
is being broadened by the exchange model.

For that matter, have you tried one of the other exchange models?

You might also consider using the remaining parameters in the
POTENTIALS list.  I don't quite remember how the default angular
comentum maxima are determined, but if might be helpful to include
more l states.

Perhaps one of the Seattle folk has some better ideas...?


On Thursday 28 August 2008 04:42:31 Janine GRATTAGE wrote:
> I have been trying to reproduce the XANES spectrum of a titanium
> compound (titanium phthalocyanine dichloride) using FEFF 8.4. The
> overall shape is reproduced reasonably well, but I wanted to ask the
> mailing list users if they have any ideas as to how to improve the
> details such as the pre-edge (to give two distinct peaks) and peak
> positions over the absorption edge.
> I have attached a file showing the experimental spectrum, two FEFF input
> files and the corresponding XMU output files. These two files have the
> same atomic co-ordinates for the molecule, but one has 'standard'  
> broadening and the Fermi level has been shifted by -1eV (geom1) where
> the other has reduced experimental broadening (-3) a shifted Fermi
> level, and smaller step size (geom1acc).
> I have tried changing the geometry of the molecule by moving one or both
> of the Cl atoms, and by trying a flat molecular geometry rather than the
> 'umbrella' shape in the attached files, but the spectra attached are the
> best match to experiment. Any help or suggestions on improvements would
> be greatly appreciated.

 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

 My homepage:    http://xafs.org/BruceRavel
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/

More information about the Ifeffit mailing list