## calculation of DOS for antiferromagnetic Fe2O3

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zzhlax
Newbie
Posts: 28
Joined: Mon Jun 29, 2009 6:41 am
License Nr.: Medea via Materials Design

### calculation of DOS for antiferromagnetic Fe2O3

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.
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
Full Member
Posts: 105
Joined: Tue Oct 12, 2010 11:10 pm

### Re: calculation of DOS for antiferromagnetic Fe2O3

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

### Re: calculation of DOS for antiferromagnetic Fe2O3

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
Newbie
Posts: 28
Joined: Mon Jun 29, 2009 6:41 am
License Nr.: Medea via Materials Design

### Re: calculation of DOS for antiferromagnetic Fe2O3

kambiz wrote: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,

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
Newbie
Posts: 28
Joined: Mon Jun 29, 2009 6:41 am
License Nr.: Medea via Materials Design

### Re: calculation of DOS for antiferromagnetic Fe2O3

Neutrino wrote: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.