[Ifeffit] Help with cif file

Wed Aug 18 01:36:03 CDT 2010

Dear Kleper,

even though I haven't tested it in detail, I'm sure the errors come from the fact that ATOMS cannot handle site occupancies other than unity. If you have a look in the cif file, you can see that both W (0.23) and Ti (0.54) have a fractional occupancy:

loop_
_atom_site_label
_atom_site_type_symbol
_atom_site_symmetry_multiplicity
_atom_site_Wyckoff_symbol
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_attached_hydrogens
_atom_site_calc_flag
  W1    W4+    4 e 0. 0. 0.0564(2) 0.23  0 d
  Ti1   Ti4+   2 a 0. 0. 0. 0.54  0 d
  O1    O2-    4 f 0.3007(6) 0.3007(6) 0. 1.  0 d

To get it working, you need to use the prototypical structure (e.g. TiO2) without mixed sites as ATOMS input. In the feff.inp file, you can then change 46 out of 100 Ti atoms to W (5 out of 10 should be ok as well for a smaller cluster). Don't forget to add the appropriate POTENTIALS line for W to the feff.inp. The small shift of the W atoms away from the Ti positions then could be handled by some additional delR parameter for the W paths during fitting. 

All the best,
Dominik

Am 17.08.2010 um 15:27 schrieb Kleper Rocha:

> 
> Please,
> 
> Could someone help me with the cif file attached, get from the www.crystallographic.net shearch with the terms Ti, W, O. When I try to run the Feff the following message appears.
> 
> "Feff 6L.02
>   WARNING:  TWO ATOMS VERY CLOSE TOGETHER.  CHECK INPUT.
>    atoms     1    2
>      1    0.00000    0.00000    0.00000
>      2    0.00000    0.00000   -0.16378
>   Run continues...
>   WARNING:  TWO ATOMS VERY CLOSE TOGETHER.  CHECK INPUT.
>    atoms     1    3
>      1    0.00000    0.00000    0.00000
>      3    0.00000    0.00000   -0.32756
>   Run continues...
>   WARNING:  TWO ATOMS VERY CLOSE TOGETHER.  CHECK INPUT.
>    atoms     2    3
>      2    0.00000    0.00000   -0.16378
>      3    0.00000    0.00000   -0.32756
>   Run continues...
>   WARNING:  TWO ATOMS VERY CLOSE TOGETHER.  CHECK INPUT.
>    atoms    10   11
>     10    0.00000    0.00000    2.57634
>     11    0.00000    0.00000    2.74012
>   Run continues...
>   WARNING:  TWO ATOMS VERY CLOSE TOGETHER.  CHECK INPUT.
>    atoms    10   12
>     10    0.00000    0.00000    2.57634
>     12    0.00000    0.00000    2.90390
>   Run continues...
>   WARNING:  TWO ATOMS VERY CLOSE TOGETHER.  CHECK INPUT.
>    atoms    11   12
>     11    0.00000    0.00000    2.74012
>     12    0.00000    0.00000    2.90390
>   Run continues...
>   WARNING:  TWO ATOMS VERY CLOSE TOGETHER.  CHECK INPUT.
>    atoms    13   14
>     13    0.00000    0.00000   -2.90390
>     14    0.00000    0.00000   -3.06768
>   Run continues...
>  Titanium tungsten oxide (0.54/0.46/2)
>  Ti.54 W.46 O2
>  O2 Ti0.54 W0.46
>  Peters, E.
>  Ueber ein niedervalentes Titan-Wolframoxid: Ti0,54 W0,46 O2
>  Calculating potentials and phases...
>      free atom potential and density for atom type    0
>      free atom potential and density for atom type    1
>      free atom potential and density for atom type    2
>      free atom potential and density for atom type    3
>      overlapped potential and density for unique potential    0
>      overlapped potential and density for unique potential    1
>      overlapped potential and density for unique potential    2
>      overlapped potential and density for unique potential    3
>      muffin tin radii and interstitial parameters
> 
> 
>     This warning indicates a problem in the Atoms list.  For some
>     reason you have atoms that are separated by than 0.93 Angstroms
>     (or 1.75 Rydberg).
> 
>     This may be due to the presence of hydrogen atoms in your feff.inp
>     file, in which case this is an innocuous warning and may be ignored.
> 
>     However, this may indicate a problem constructing the Atoms
>     list. The most common cause of this problem is a mistake in the
>     crystallographic data used on the Atoms page.  You may have
>     incorrect values for lattice constants or angles or incorrect
>     values for site coordinates.  You may need a shift vector to move
>     the lattice into its standard setting.
> 
>     Please be aware that Atoms works with 5 digits of precision.
>     Thus, if you have a site with a coordinate of 1/3, you should use
>     either "1/3" or "0.33333" on the Atoms page.  Using insufficient
>     precision, say "0.333" is a common cause of this error message.
> 
>     Artemis has continued on the possibility that the warning is
>     caused by hydrogen atoms, but be warned that the feff.inp may
>     require your attention."
> 
> Thanks in advance.
> 
> 
> 
> Kleper de Oliveira Rocha
> 
> <O2 Ti0.54 W0.46.cif>_______________________________________________
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-- 
Dr. Dominik Samuelis
d.samuelis at fkf.mpg.de
Max-Planck-Institut für Festkörperforschung
Heisenbergstr. 1
70569 Stuttgart
Germany
Phone +49-711-689-1769
Fax   +49-711-689-1722
Web http://www.fkf.mpg.de/maier/