calculation of DOS for antiferromagnetic Fe2O3

[zzhlax]

Dear everyone,

when performing DOS calculations on antiferromagnetic Fe2O3, I found the symmetry of system affected the resulted DOS. if the symmetry was swithced on (ISYM = 2, PAW potential), the spin-up and spin-down DOS were asymmetric. however, if the symmetry was swithed off, they were symmetric, just as reported in the literature. I feel a little confused why the symmetry should be cancelled to obtain a reasonable DOS.

So, any suggestion will be highly appreciated.
Thanks!

Zhaohui

INCAR:
SYSTEM = Fe2O3:AF
PREC = Accurate
ENCUT = 400
IBRION = -1
NSW = 0
EDIFFG = -0.01
NELM = 60
NELMIN = 2
EDIFF = 1.0e-05
VOSKOWN = 1
NBLOCK = 1
ALGO = Normal
ISPIN = 2
MAGMOM = 6*0 -5 5 5 -5
INIWAV = 1
ISTART = 0
ICHARG = 2
LWAVE = .FALSE.
LCHARG = .TRUE.
ADDGRID = .FALSE.
LVTOT = .FALSE.
ISMEAR = -5
SIGMA = 0.1
LREAL = .FALSE.
NPAR = 12
LORBIT = 11

POSCAR:
Fe2O3:AF
1.00000000000000
5.4530725568820815 0.0290078138252294 0.0198333915443075
3.1297067358126336 4.4656217385034269 0.0198333915442548
3.1297067358124129 1.6389647112017331 4.1540300372047891
O Fe
6 4
Direct
0.4404640047971737 0.7500000000000000 0.0595360542028276
0.9404639457971724 0.5595359952028263 0.2500000000000000
0.7500000000000000 0.0595360542028276 0.4404640047971737
0.2500000000000000 0.9404639457971724 0.5595359952028263
0.0595360542028276 0.4404640047971737 0.7500000000000000
0.5595359952028263 0.2500000000000000 0.9404639457971724
0.1440321266347607 0.1440321266347607 0.1440321266347607
0.3559678733652394 0.3559678733652394 0.3559678733652394
0.6440321266347608 0.6440321266347608 0.6440321266347608
0.8559678733652392 0.8559678733652392 0.8559678733652392

[kambiz]

Hi,

Your question is a bit vague. If I correctly understated it, the total magnetic moment is zero no matter ISYM is on or off (Am I right ?) or It is only zero when ISYM = 0 ?

Anyway, If Fe2O3 is anti-ferromagnetic, my suggestion is to use ISYM = 0 to exclude the effect of symmetry constraints.

Cheers

[Neutrino]

It seems you are getting Ferrimagnetic results with ISYM=2 and Antiferromagnetic results with ISYM=0. Ideally you should remove all symmetry constraints by setting ISYM=0 to obtain the lowest energy structure. A more convencing argument is that if the Antiferromagnetic structure has lower energy then ISYM=0 helped to reach to a more thermodynamically stable structure.

[zzhlax]

Hi,

Your question is a bit vague. If I correctly understated it, the total magnetic moment is zero no matter ISYM is on or off (Am I right ?) or It is only zero when ISYM = 0 ?

Anyway, If Fe2O3 is anti-ferromagnetic, my suggestion is to use ISYM = 0 to exclude the effect of symmetry constraints.

Cheers

Dear Kambiz,

Thanks for your suggestion.

In my calculation, no matter ISYM is on or off, the total magnetic moment is zero (anti-ferromagnetic). The difference is, when ISYM=2 DOS is asymmetric, while DOS is symmetric with ISYM=0.

Cheers,

[zzhlax]

It seems you are getting Ferrimagnetic results with ISYM=2 and Antiferromagnetic results with ISYM=0. Ideally you should remove all symmetry constraints by setting ISYM=0 to obtain the lowest energy structure. A more convencing argument is that if the Antiferromagnetic structure has lower energy then ISYM=0 helped to reach to a more thermodynamically stable structure.

Dear Neutrino,

No matter ISYM is on or off, I got a total magnetic moment of zero, almost identical total energy and equal munber of Fe atoms with opposite spin. I think that means I got an anti-ferromagnetic ground state with ISYM on or off. What makes me feel confused is when ISYM=2, DOS is asymmetric slightly and when ISYM=0, DOS is symmetric totally.

Thanks for your attention.

Best wishes,