[Ifeffit] Problem with running FEFF in Artemis

[Bruce Ravel]

On Friday, April 15, 2011 09:14:00 am Jatinkumar Rana wrote:
> Dear Ifeffit users,
> 
>   I am facing a strange problem in running ATOMS for the "F d-3 m" space
> group. It gives me following message :
> 
>   "F d -3 m" appears in the International Tables with
>    multiple choices of origin.  If the atoms list seems wrong, you
>    should use a shift vector of:
>      -0.125, -0.125, -0.125


Crystals in that space group are sometimes referenced to one choice of
origin (i.e. one particular center of symmetry) and sometimes
referenced to another.  Atoms has no way of knowing what choice the
authors of any particular crystal structure might have made, so it is
kind enough to alert you to this common issue.

In the event that the structure in the feff.inp file looks wrong with
a shift verctor of (0,0,0), atoms is kind enough to suggest a likely
solution.  It did not issue a command -- you are not required to apply
a non-zero shift vector.  It's a suggestion in the case of trouble. :)

To my eye, the feff.inp file with shift = (0,0,0) looks plausible.
The feff.inp file with shift = (-1/8,-1/8,-1/8) is clearly wrong, as
you point out.

So, is the shift=(0,0,0) feff.inp file not right?

B

 
> After i add shift vector on ATOMS page and run FEFF in ARTEMIS, it gives
> me error and shows that many pairs of atoms are close together. The
> crystallographic data used to run FEFF were obtained using Neutron
> diffraction experiments. I do not understand the reason for this since i
> have never come across such a problem.
> 
> Can anyone help me to comeout of this problem ?
> 
> I have attached the Artemis project file with this mail for further detail.
> 
> With best regards,
> Jatin Rana
> Berlin

-- 

 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

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