[Ifeffit] LDOS calculations

prange prange at u.washington.edu
Wed Apr 30 12:13:12 CDT 2008


One should be able to achieve reasonable agreement between the  
electronic structure calculated with VASP and FEFF. Here are a couple  
of things you might consider to improve agreement.

1) Do the FEFF calculation with NOHOLE. This should give ground-state  
LDA DOS that is comparable to standard DFT codes. You can compare  
ldos00.dat and ldos02.dat to see the effect of the hole.

2) Make sure you have aligned the energy grids appropriately. The 0  
of the FEFF energy grid is the vacuum energy; the Fermi level is  
reported in the header of ldsoNN.dat -- for an insulator this should  
be close to a dip in the total DOS which is the gap. Using a larger  
cluster (and rfms) in the FEFF cluster will make the gap more  
defined. Once the gaps are aligned, other features should also match.

3) Broaden the DOS from VASP. This will make comparison much easier.

4) Make sure you are comparing the total DOS (i.e. the sum of  
ldos01.dat+2*ldos02.dat) in the same units. The FEFF DOS is in states/ 
eV/site, so you will need to account for the number of atoms of each  
species in the unit cell and perhaps convert from eV to hartrees.

Good luck,

Micah Prange

On Apr 30, 2008, at 9:51 AM, Rajdeep Saha wrote:
> I calculate the DOS of TiO_2 anatase system using FEFF8 and then  
> compare the
> results with benchmark calculations done using VASP. Apparently,  
> the FEFF
> results are no where near the VASP results. I was wondering if  
> somebody could
> take a look at my input file and suggest some improvements. I am  
> absolutely new
> to EXAFS, and anybody's help would be greatly appreciated.
> Thanks,
> Rajdeep Saha.

More information about the Ifeffit mailing list