Hi All, This question concerns the Feff8 program. So this may not be the appropriate site, however I would greatly appreciate if I could get some feedback. 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. The input file is as follows; TITLE anatase HOLE 1 1.0 CONTROL 1 1 1 0 0 0 PRINT 0 0 0 0 0 0 RPATH 5.5 LDOS -18 0 0.01 SCF 6.21 POTENTIALS 0 8 O 1 22 Ti 2 8 O ATOMS 5.67630000 5.67630000 14.27190000 1 Ti 5.67630000 5.67630000 4.75730000 1 Ti 5.67630000 3.78420000 16.65055000 1 Ti 5.67630000 3.78420000 7.13595000 1 Ti 5.67630000 1.89210000 14.27190000 1 Ti 5.67630000 1.89210000 4.75730000 1 Ti 5.67630000 0.00000000 16.65055000 1 Ti 5.67630000 0.00000000 7.13595000 1 Ti 3.78420000 5.67630000 11.89325000 1 Ti 3.78420000 5.67630000 2.37865000 1 Ti 3.78420000 3.78420000 9.51460000 1 Ti 3.78420000 3.78420000 0.00000000 1 Ti 3.78420000 1.89210000 11.89325000 1 Ti 3.78420000 1.89210000 2.37865000 1 Ti 3.78420000 0.00000000 9.51460000 1 Ti 3.78420000 0.00000000 0.00000000 1 Ti 1.89210000 5.67630000 14.27190000 1 Ti 1.89210000 5.67630000 4.75730000 1 Ti 1.89210000 3.78420000 16.65055000 1 Ti 1.89210000 3.78420000 7.13595000 1 Ti 1.89210000 1.89210000 14.27190000 1 Ti 1.89210000 1.89210000 4.75730000 1 Ti 1.89210000 0.00000000 16.65055000 1 Ti 1.89210000 0.00000000 7.13595000 1 Ti 0.00000000 5.67630000 11.89325000 1 Ti 0.00000000 5.67630000 2.37865000 1 Ti 0.00000000 3.78420000 9.51460000 1 Ti 0.00000000 3.78420000 0.00000000 1 Ti 0.00000000 1.89210000 11.89325000 1 Ti 0.00000000 1.89210000 2.37865000 1 Ti 0.00000000 0.00000000 9.51460000 1 Ti 0.00000000 0.00000000 0.00000000 1 Ti 5.67630000 5.67630000 16.25188826 2 O 5.67630000 5.67630000 12.29191174 2 O 5.67630000 5.67630000 6.73728826 2 O 5.67630000 5.67630000 2.77731174 2 O 5.67630000 3.78420000 18.63053826 2 O 5.67630000 3.78420000 14.67056174 2 O 5.67630000 3.78420000 9.11593826 2 O 5.67630000 3.78420000 5.15596174 2 O 5.67630000 1.89210000 16.25188826 2 O 5.67630000 1.89210000 12.29191174 2 O 5.67630000 1.89210000 6.73728826 2 O 5.67630000 1.89210000 2.77731174 2 O 5.67630000 0.00000000 18.63053826 2 O 5.67630000 0.00000000 14.67056174 2 O 5.67630000 0.00000000 9.11593826 2 O 5.67630000 0.00000000 5.15596174 2 O 3.78420000 5.67630000 13.87323826 2 O 3.78420000 5.67630000 9.91326174 2 O 3.78420000 5.67630000 4.35863826 2 O 3.78420000 5.67630000 0.39866174 2 O 3.78420000 3.78420000 17.04921174 2 O 3.78420000 3.78420000 11.49458826 2 O 3.78420000 3.78420000 7.53461174 2 O 3.78420000 3.78420000 1.97998826 2 O 3.78420000 1.89210000 13.87323826 2 O 3.78420000 1.89210000 9.91326174 2 O 3.78420000 1.89210000 4.35863826 2 O 3.78420000 1.89210000 0.39866174 2 O 3.78420000 0.00000000 17.04921174 2 O 3.78420000 0.00000000 11.49458826 2 O 3.78420000 0.00000000 7.53461174 2 O 3.78420000 0.00000000 1.97998826 2 O 1.89210000 5.67630000 16.25188826 2 O 1.89210000 5.67630000 12.29191174 2 O 1.89210000 5.67630000 6.73728826 2 O 1.89210000 5.67630000 2.77731174 2 O 1.89210000 3.78420000 18.63053826 2 O 1.89210000 3.78420000 14.67056174 2 O 1.89210000 3.78420000 9.11593826 2 O 1.89210000 3.78420000 5.15596174 2 O 1.89210000 1.89210000 16.25188826 2 O 1.89210000 1.89210000 12.29191174 2 O 1.89210000 1.89210000 6.73728826 2 O 1.89210000 1.89210000 2.77731174 2 O 1.89210000 0.00000000 18.63053826 2 O 1.89210000 0.00000000 14.67056174 2 O 1.89210000 0.00000000 9.11593826 2 O 1.89210000 0.00000000 5.15596174 2 O 0.00000000 5.67630000 13.87323826 2 O 0.00000000 5.67630000 9.91326174 2 O 0.00000000 5.67630000 4.35863826 2 O 0.00000000 5.67630000 0.39866174 2 O 0.00000000 3.78420000 17.04921174 2 O 0.00000000 3.78420000 11.49458826 2 O 0.00000000 3.78420000 7.53461174 2 O 0.00000000 3.78420000 1.97998826 2 O 0.00000000 1.89210000 13.87323826 2 O 0.00000000 1.89210000 9.91326174 2 O 0.00000000 1.89210000 4.35863826 2 O 0.00000000 1.89210000 0.39866174 2 O 0.00000000 0.00000000 17.04921174 2 O 0.00000000 0.00000000 11.49458826 2 O 0.00000000 0.00000000 7.53461174 2 O 0.00000000 0.00000000 1.97998826 0 O
Rajdeep, 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.
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Rajdeep Saha