My Community

Dear all,

Following the guidelines given in the Vasp guide http://cms.mpi.univie.ac.at/vasp/vasp/D ... atoms.html, I have tried to calculate the total energy of the Ni free atom. My input files are as below:

POSCAR -----------
1
13.0 00.0 00.0
00.0 14.0 00.0
00.0 00.0 15.0
1
direct
0.0 0.0 0.0

KPOINTS ----------
1
rec
0 0 0 1

INCAR ------------
ISYM = 0
ISPIN = 2
ISMEAR = 0
SIGMA = 0.002
AMIX = 0.2
BMIX = 0.0001
ICHARG = 1
ENCUT=600
EDIFF=0.00000001
ALGO = A ; LSUBROT = .FALSE. ; NELM = 500 ; TIME = 0.2

And I used the pbe_paw POTCAR.

I executed VASP three times and the total energy was converged, but I ended up with fractional occupancies:

spin component 1

k-point 1 : 0.0000 0.0000 0.0000
band No. band energies occupation
1 -6.3009 1.00000
2 -5.6743 1.00000
3 -5.5825 1.00000
4 -5.3029 1.00000
5 -5.3028 1.00000
6 -4.9296 1.00000
7 -1.0534 0.00000
.
.
.
spin component 2

k-point 1 : 0.0000 0.0000 0.0000
band No. band energies occupation
1 -4.7026 1.00000
2 -4.4841 1.00000
3 -4.4840 1.00000
4 -4.1190 0.70933
5 -4.1174 0.29067
6 -3.9445 0.00000
8 -0.2898 0.00000

Any suggestions to solve this problem?

Moreover, in the POTCAR file, the valence electron configuration (VRHFIN) of Ni is not given:

PAW_PBE Ni 06Sep2000
10.0000000000000000
parameters from PSCTR are:
VRHFIN =Ni:
LEXCH = PE
EATOM = 1077.9025 eV, 79.2236 Ry

Why is it like that for Ni? And what is the configuration?

Thank you in advance ..

Hi,

have you considered to freeze the spin state with NUPDOWN ?

Cheers,

alex

Dear Alex,
Thank you very much!

I used (NUPDOWN = 2) in the INCAR but I got exactly the same result!

I think NUPDOWN controls the "difference" between number of electrons in up and down spin component. This was controlled properly in my case, despite the existence of fractional occupancies!

When I used (NUPDOWN = 1), I got fractional occupancies in both up and down spin components, while the "difference" was exactly 1 !

Please, let me know if I misunderstand something ..

Cheers

Hi,
I think setting SIGMA=0 could help, or setting the occupancies manually with
FERWE= 6*1 N*0 (N is the NBANDS-NOCCUPIED and NOCCUPIED in your case is 6)
FERDO=4*1 (N+2)*0
either of this might work

Best
jik