My Community

I was doing maybe the most simple test. One isolated Rh atom using a simple INCAR, a big box, GGA, and just Gamma point.

ISPIN = 2
VOSKOWN = 1
ISMEAR = 0 (Gaussian)
SIGMA = 0.01
LORBIT = 10

As expected, everything seems to be all right and well converged....
BUT when I set up

NUPDOWN = 3

flag in the INCAR file I got clear discrepancies in the DOSCAR file. The integrated DOS(up) and integrated DOS(dwn) seem to be wrong. In the DOSCAR file I am getting 16 electrons and of course also the height of the discrete spectrum (DOS) change. Well, the location of the picks are correct. Taking a look in the OUTCAR file, in both cases the number of electrons is equal to 9 and the magnetization equal to 3 as expected, also, the occupation for each band is 1.

Here an small portion of the wrong DOSCAR file around the fermi energy,

E_Fermi = -5.20709742
...
-5.320 0.0000E+00 0.0000E+00 0.1000E+02 0.0000E+00
-5.293 0.0000E+00 0.3518E-04 0.1000E+02 0.9333E-06
-5.267 0.0000E+00 0.1949E+02 0.1000E+02 0.5172E+00
-5.240 0.0000E+00 0.2047E+03 0.1000E+02 0.5949E+01
-5.214 0.0000E+00 0.1918E+01 0.1000E+02 0.6000E+01
-5.187 0.0000E+00 0.9359E-07 0.1000E+02 0.6000E+01
-5.161 0.0000E+00 0.0000E+00 0.1000E+02 0.6000E+01
...

Of course, if I remove the NUPDOWN variable I recover the correct number of electrons, intDOS(up) = 6, intDOS(dwn)=3. Maybe it is important to say that I also try an additional "static" run using NSW = 0 and ISTART = 1 to calculate DOSCAR, even when I think it is not necessary to do it because the FFT-grid has not changed. I also try Rh_1, Rh_2, Co_1, and Co_2 with the same wrong results.

Here my question is, is there any dependence of the DOSCAR file with respect to NUPDOWN? Maybe something missing?

I am using version vasp.5.2.2

Thank you very much in advance for any clarification at this respect.

Luis

PS. I try to do an intensive search in the forum but I did not find any answer. I apologize in case some one else answer this question before.

if NUPDOWN is set,
1) the Fermi level is calculated from the electrons which are set to spin down explicitely (and it is not adjusted to the spin-up window again)
2) the weight factors in the integrated DOS are multiplied by 2.
However, for a free Rh atom (as you report)
-- the results are basically thes same, independent of whether NUPDOWN is set (proveided that you converge to the electronic
ground state of the free atom, following Hund's rune)
-- free atoms have a discrete line sprectrum, not a DOS. Therefore it is more appropriate to check the KS-levels.

--

Perfect, clear!

Thanks a lot!
<span class='smallblacktext'>[ Edited Thu May 27 2010, 09:10PM ]</span>