[Ifeffit] A problem Using FEFF8

Joshua Kas joshua.j.kas at gmail.com
Thu Mar 25 02:06:17 CDT 2010


Hi Qui Nan,
There are several other parameters to the SCF card that may help.

Try the following,

* SCF    rscf     lscf     niter     ca     nmix
  SCF    8.0      0         30       0.05   0

ca is the convergence factor in the Broyden algorithm. A lower value of ca
will stabilize the SCF, but cause slower convergence. nmix is the number of
iterations using the mixing algorithm before starting the Broyden algorithm.
I have found that this is usually where the bad counts problem occurs, which
is why I set it to 0. If this still doesn't work, try other values for the
ca and nmix parameters.
I have found that changing the ca and nmix parameters will usually (not
always) fix the problem.
Please email the list again if you continue to have problems.
Cheers,
Josh Kas

> Dear Mr. Bruce,
>     My name is QIU Nan, I am a student from Institute of High Energy
> Physics, Chinese Academy of Science.
>    I encountered a preblem When I calculated O K edge of cerium oxide(CeO2)
> using FEFF8.  FEFF found bad counts:  Occupation number in getorb is  4.000
> , then FEFF repeated  pteration again and again. The attached files are
> feff.inp I used and log1.dat that FEFF generated. Would you so kind to help
> me to finish this calculation?
>     Best Wishes!
>      QIU Nan
>    2010-03-24
>
>
>
>
> -------------------------------------------------------
> --
>  Bruce Ravel  ----------------------------------- bravel at bnl.gov
>
>  National Institute of Standards and Technology
>  Synchrotron Measurements Group, Beamlines X23A2, X24A, U7A
>
>  Building 535A, Room M7
>  Brookhaven National Laboratory
>  Upton NY, 11973, USA
>
>  My homepage:    http://xafs.org/BruceRavel
>  EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/
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