[Ifeffit] lanthanides convergence

Thu Sep 4 22:00:54 CDT 2008

Hi Joshua,

I can not find convergence on the absorption spectra. It is very hard to
believe that 500 atoms is not enough to find a converged spectra.

If I increase the broadening for the LDOS, the default is 0.1eV for the one
exported by Arthemis and 0.2eV is shown in the manual, the last one is still
small compared with 4.16 eV. Which is a good criteria to choose it and where
I can find the core hole broadening value?

I will quit the LDOS card to obtain results faster, but pot.bin will be
generated anyway (I will leave the CONTROL card option on), if not, is it
needed for another calculation? The calculations (without the LDOS) and the
spectra will be obtained like before?

I will implement the lanczos algorithm too and parameter nex to obtain
faster results with a bigger number of atoms.

Cheers, euG

8<- - - - - - 8<- - - - - - 8<- - - - - - 8<- - - - - -

Lic. Eugenio H. Otal
E-mail: eotal at citefa.gov.ar
          eugenioh at gmail.com

8<- - - - - - 8<- - - - - - 8<- - - - - - 8<- - - - - -

Hi Eugenio,
I have a question for you,
When you say that convergence is not reached, do you mean convergence of
the absoption spectrum or convergence of the LDOS? These are very
different since the absorption has core-hole and self-energy broadening
included. I noticed that you use 0.1 eV broadening for the LDOS, which is
much smaller than the core hole broadening which is 4.16eV. Also, the
calculation will be much quicker if you do not run LDOS since FEFF
does the matrix inversion for each unique potential and energy when the
LDOS card is present. Otherwise, the inversion is only done for the
central atom potential at each energy.
Cheers,
Josh Kas

>
> Bruce,
>
> thanks for your answer, it is a great problem to increase the number of
> atoms, huge CPU time is needed to finish a calculation.
>
> Here I pasted the header and the first lines of the atom list and attached
> the whole file, if somebody could help me to reduce the calculation time I
> will be grateful.
>
> Thanks in advance, euG
>
> * This feff8 input file was generated by Artemis 0.8.011
> * Atoms written by and copyright (c) Bruce Ravel, 1998-2001
>
> TITLE name: ZnO:Er 1 at no distortion d= 4.136
> TITLE formula: ZnO
> TITLE sites: Zn1,O1
> TITLE refer1: wyckoff, vol 1, ch III, p 111
> TITLE refer2:
> TITLE schoen:
> TITLE notes1:
>
> * Er L3 edge energy = 8358.0 eV
> EDGE L3
> S02 1.0
>
> * pot xsph fms paths genfmt ff2chi
> CONTROL 1 1 1 1 1 1
> PRINT 3 0 0 0 0 0
>
> *** ixc=0 means to use Hedin-Lundqvist
> * ixc [ Vr Vi ]
> EXCHANGE 0
>
> *** Radius of small cluster for
> *** self-consistency calculation
> *** A sphere including 2 shells is
> *** a good choice
> *** l_scf = 0 for a solid, 1 for a molecule
> * r_scf [ l_scf n_scf ca ]
> SCF 4.0
>
> *** Upper limit of XANES calculation.
> *** This *must* be uncommented to
> *** make Feff calculate full multiple
> *** scattering rather than a path expansion
> * kmax [ delta_k delta_e ]
> XANES 4.0
>
> *** Radius of cluster for Full Multiple
> *** Scattering calculation
> *** l_fms = 0 for a solid, 1 for a molecule
> * r_fms l_fms
> FMS 5.00 0
>
> *** Energy grid over which to calculate
> *** DOS functions
> * emin emax eimag
> LDOS -30 20 0.1
>
> *** for EXAFS: RMAX 12.0 and uncomment
> *** the EXAFS card
> RPATH 0.1
> *EXAFS 20
>
> POTENTIALS
> * ipot Z element l_scmt l_fms stoichiometry
> 0 68 Er 3 3 0.001
> 1 30 Zn 2 2 2
> 2 8 O 1 1 2
> 3 68 Er 3 3 2
>
> ATOMS * this list contains 902 atoms
> * x y z ipot tag distance
> 0.00000 0.00000 0.00000 0 Er 0.00000 0
> -0.93804 -1.62473 -0.49466 1 Zn1 1.94019 1
> 1.87611 0.00002 -0.49466 1 Zn1 1.94023 2
> -0.93804 1.62477 -0.49466 1 Zn1 1.94023 3
> -0.93804 -1.62473 1.30173 2 O1 2.28346 4
> 0.93804 1.62473 -1.30173 2 O1 2.28346 5
> 1.87611 0.00002 1.30173 2 O1 2.28348 6
> -0.93804 1.62477 1.30173 2 O1 2.28348 7
> -1.87611 -0.00002 -1.30173 2 O1 2.28348 8
> 0.93804 -1.62477 -1.30173 2 O1 2.28348 9
> 0.93804 1.62473 2.10879 1 Zn1 2.82253 12
> -1.87611 -0.00002 2.10879 1 Zn1 2.82255 13
> 0.93804 -1.62477 2.10879 1 Zn1 2.82255 14
> 0.93804 1.62473 -3.09811 1 Zn1 3.62187 21
> -1.87611 -0.00002 -3.09811 1 Zn1 3.62189 22
> 0.93804 -1.62477 -3.09811 1 Zn1 3.62189 23
> -3.75219 0.00002 -0.49466 1 Zn1 3.78466 24
> 1.87611 -3.24948 -0.49466 1 Zn1 3.78465 25
> 1.87611 3.24952 -0.49466 1 Zn1 3.78469 26
> -3.75219 0.00002 1.30173 2 O1 3.97158 27
> 1.87611 -3.24948 1.30173 2 O1 3.97158 28
> -1.87611 3.24948 -1.30173 2 O1 3.97158 29
> 3.75219 -0.00002 -1.30173 2 O1 3.97158 30
> 1.87611 3.24952 1.30173 2 O1 3.97161 31
> -1.87611 -3.24952 -1.30173 2 O1 3.97161 32
> 2.81415 1.62475 2.60345 3 Er 4.16380 33
> -1.87611 3.24948 2.10879 1 Zn1 4.30417 45
> 3.75219 -0.00002 2.10879 1 Zn1 4.30418 46
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