[Ifeffit] Generating single scattering paths in Artemis

Carlo U. Segre segre at iit.edu
Wed Jan 5 15:43:09 CST 2005


These are just the kind of problems I was having but I would add that for 
someone who is not savvy about crystallography, having to fake a crystal 
with a low symmetry space group is not terribly intuitive.

I agree with you also about the symmetry of the neighbors but, again, i 
think that the benefit of an intuitive interface to what the scientist 
wants to do is a good thing.  I think that having to use work-arounds is 
difficult to explain to new users.  Perhaps a new chemistry student knows 
that his/her atom has an octahedral coordination.  It woujld be good to be 
able to intuitively model that.

Just my $0.02


On Wed, 5 Jan 2005 scalvin at slc.edu wrote:

> Hi Carlo,
> Hmmm...my initial reaction was that, rather than loading Artemis with a
> new option, it's better just to "fake it" by using a low-symmetry space
> group with a large lattice parameter and then truncating the cluster size
> at smaller than the unit cell. But I just tried this, and discovered an
> interesting problem, which you may have come across as well.
> What I did was attempted to create an octahedral cluster by using a space
> group of P m 3 m (simple cubic) with a=10, an Fe at 0 0 0 absorbing, and
> an oxygen at 0.2 0 0 (thus an Fe-O distance of 2 angstroms). The cluster
> size is set at 5. As expected, that generates an octahedral cluster of
> oxygens around the Fe as a FEFF.INP file. But here's the problem: Artemis
> includes a potential for scattering atoms of Fe, and there aren't any in
> the list. FEFF, in turn, doesn't like that and won't run, causing Artemis
> to give the error message:

Carlo U. Segre -- Professor of Physics
Associate Dean for Special Projects, Graduate College
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
Carlo.Segre at iit.edu    http://www.iit.edu/~segre

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