[Ifeffit] EXAFS analysis with FEFF

Bruce Ravel bravel at anl.gov
Tue Feb 27 13:38:06 CST 2007


Hi Gemma,

I am not sure that I have the whole answer for you.  I too have had
trouble at times getting feff8 to run with hydrogen atoms in the
cluster.  I am CCing my response to the mailing lists for Feff and
Ifeffit in hopes that someone else might have some more wisdom for
you.   The feff.inp file you sent me is appended to the end of this
email, in case any of the brains on the mailing lists need to see it. 

On Tuesday 27 February 2007 11:27, Gemma GUILERA wrote:
> I am currently running FEFF8.2 for one of my systems which include some H
> atoms (as hydrides). These are actually very important in the structure and
> I want to consider them in the run.
> For this I used the FOLP function in POT  with an overlapping value of 0.8
> for H as suggested in the manual. Also, since I think that the AFOLP card
> gets deactivated, I also added these cards for the rest of the potentials
> keeping them at 1.15.
> I obviously do something completely wrong because the program stops and
> appears an error message of the type:
>
> FOLP for POTENTIAL type   0 is too big.
>   Reduce overlap using FOLP and rerun.
>
> I do not understand what I need to do, because the potential 0 is not the
> one I am modifying with respect to the default values.
> I would really appreciate if you could have a look at the feff.inp file and
> tell me what did I do wrongly...and sorry for wasting your time.

Well, my understanding is that Feff's various overlapping methods do
have effects that are not restricted to the ipots that you are
explicitly modifying.  That is, if you restrain the size of one muffin
tin, other muffin tins can get a bit bigger or smaller to compensate.
It depends on the geometry and how the atom you are modifying is
represented in the cluster.

My first thought is that you need to play around with the FOLP value
for the absorber.  Try smaller values to see if you can get Feff to
run to completion.

My second thought is to abandon the FOLP keywords and try using
AFOLP. 

Another thought is that you may need to use a larger cluster.  Some
atom types -- B for example -- have few representatives in your
cluster and so their muffin tin radii might be improperly constrained.

Does anyone else have any good suggestions for Gemma?

B



 
 TITLE   FeBH6Fe complex
  
 EDGE      K
 S02       1.0

 *         pot    xsph  fms   paths genfmt ff2chi
 CONTROL   1      1     1     1     1      1
 PRINT     1      0     0     0     0      3
  
 *         r_scf   [ l_scf  n_scf  ca ]
 SCF       2.90160   0      15     0.1

 *         ixc  [ Vr  Vi ]
 EXCHANGE  0      0   0

 FOLP  0  1.15
 FOLP  1  0.8   !Use 0.8 muffin-tin radii overlapping factor for H
 FOLP  2  1.15
 FOLP  3  1.15
 FOLP  4  1.15
 FOLP  5  1.15

 EXAFS
 RPATH     6

 *         kmax  [ delta_k  delta_e ]
 *XANES     4.0     0.07     0.5
 *         r_fms     [ l_fms ]
 *FMS       2.90160     0
 *
 *RPATH     0.10000
 *         emin  emax  resolution
 *LDOS      -20    20   0.1

 POTENTIALS
 *   ipot   z [ label   l_scmt  l_fms  stoichiometry ]
       0   26    Fe     -1      -1       0
       1    1    H      -1      -1       6
       2    5    B      -1      -1       1
       3   15    P      -1      -1       6
       4    6    C      -1      -1      46
       5   26    Fe     -1      -1       2
  
 ATOMS
   0.00000     0.00000     0.00000    0   Fe1              0.00000
  -0.71680    -1.08741    -0.20797    1   H42              1.31891
  -1.33000     0.40717     0.04190    1   H41              1.39156
  -0.20933    -0.03121    -1.56977    1   H40              1.58398
  -1.50973    -0.47766    -1.07196    2   B1               1.91221
   0.07929    -0.26849     2.16349    3   P3               2.18152
   0.78129     2.03650     0.10939    3   P2               2.18397
   2.03623    -0.76920    -0.20440    3   P1               2.18625
  -2.30265     0.13209    -1.93594    1   H42              3.01123
  -2.81012    -0.92412    -0.57414    1   H40              3.01338
  -1.68946    -1.36249    -2.18581    1   H41              3.08033
   3.15055    -0.21476     1.16774    4   C22              3.36686
   0.19242    -2.02477     2.69082    4   C25              3.37301
   2.87884    -0.31857    -1.75462    4   C13              3.38643
   1.52559     0.58481     2.96848    4   C24              3.38840
   2.32803     2.20201     1.14003    4   C49              3.40121
  -0.35734     3.30346     0.81773    4   C37              3.42188
   1.28771     2.89227    -1.43362    4   C43              3.47544
   2.68114     0.97735     2.02827    4   C23              3.50109
  -1.29194     0.30124     3.24246    4   C31              3.50334
   2.42741    -2.57443    -0.17395    4   C1               3.54263
   1.08472     2.33572    -2.68697    4   C48              3.72183
  -2.31005     1.13130     2.75352    4   C36              3.76803
  -3.01946    -0.95533    -2.14391    5   Fe1              3.82441
  -0.91239    -2.83347     2.42108    4   C26              3.83701
   1.44841    -3.56032    -0.07829    4   C3               3.84446
   2.35340    -0.84952    -2.93358    4   C15              3.85565
  -1.36594     3.79736    -0.00896    4   C38              4.03557
  -0.32880     3.71800     2.14367    4   C42              4.30429
   1.32048    -2.62656     3.24943    4   C30              4.38193
   3.96885     0.55229    -1.84177    4   C21              4.41009
   1.89033     4.15594    -1.34798    4   C44              4.76049
  -1.27608     0.01031     4.60350    4   C32              4.77710
   3.77855    -2.96794    -0.18652    4   C11              4.80842
   3.85573     1.40280     2.91662    4   C50              5.03400
  -4.10418    -3.29104     0.54306    4   C48              5.28868
  -3.80075    -2.99182    -2.25330    3   P2               5.33611
  -3.09875    -0.68684    -4.30740    3   P3               5.35048
  -2.10707     1.87815    -4.56499    4   C26              5.36715
  -0.70940    -2.08663    -4.89743    4   C36              5.37049
  -5.05569    -0.18613    -1.93951    3   P1               5.41815
  -5.37286    -0.10580     0.78966    4   C15              5.43161
  -1.65351    -4.75268    -2.13495    4   C38              5.46627
  -4.46787     2.60499    -2.06562    4   C3               5.56908
  -1.72752    -1.25656    -5.38637    4   C31              5.79450
  -4.30717    -3.84760    -0.71029    4   C43              5.81895
  -2.66211    -4.25879    -2.96164    4   C37              5.83056
  -3.21187     1.06944    -4.83473    4   C25              5.90207
  -5.89830    -0.63676    -0.38929    4   C13              5.94533
 END



-- 
 Bruce Ravel  ---------------------------------------------- bravel at anl.gov

 Molecular Environmental Science Group, Building 203, Room E-165
 MRCAT, Sector 10, Advanced Photon Source, Building 433, Room B007

 Argonne National Laboratory         phone and voice mail: (1) 630 252 5033
 Argonne IL 60439, USA                                fax: (1) 630 252 9793

 My homepage:    http://cars9.uchicago.edu/~ravel 
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/




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