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magnetic moments in antiferromagnetic material are zero with ISPIN=2, both finite with SOC
Posted: Thu Dec 01, 2022 2:48 pm
by sophie_weber
Hello,
I have run into this odd phenomena with two or more materials (to be specific, right now I'm looking at a (010) slab of rock-salt NiO), and was curious if anyone knows might be going on. NiO is of course an antiferromagnetic material, however, when I run an scf calculation in VASP with collinear magnetism (ISPIN=2) and set the MAGMOM flag in the INCAR to finite AFM values for the Ni atoms, when I look at the final site-projected magnetization in the OUTCAR file the moments become zero to within 0.001 uB (interestingly, for the case of NiO bulk, the moments remain what they should be, ~ 2 uB). However, when I switch SOC on for the (010) NiO slab but still set the MAGMOM flag to a collinear AFM order, and keep all other settings the same, now the converged moments in the OUTCAR are the appropriate size for Ni.
Has anyone experienced this phenomenon of atomic site moments going to zero (when they definitely should not) for an ISPIN=2 calculation, but not for the same calculation with spin-orbit coupling switched on? I can provide input files if necessary.
Thank you in advance for your help.
Re: magnetic moments in antiferromagnetic material are zero with ISPIN=2, both finite with SOC
Posted: Fri Dec 02, 2022 9:08 am
by merzuk.kaltak
Dear Sophie,
please provide some input (and possibly output files, i.e. OUTCAR and stdout).
Re: magnetic moments in antiferromagnetic material are zero with ISPIN=2, both finite with SOC
Posted: Fri Dec 02, 2022 11:49 am
by sophie_weber
Hello,
Sure; attached are tar files with the input files + OUTCAR for the case with no SOC (zero site-projected moments in the OUTCAR) and with SOC (finite, as-expected magnetic moments in OUTCAR). This particular SOC calculation is using constrained magnetism, so I'm running an SOC calculation without constraints to verify I get the same outcome, but based on this happening with previous materials I'm quite confident it will be the same.
Thank you so much for your help, I look forward to hearing back!
Re: magnetic moments in antiferromagnetic material are zero with ISPIN=2, both finite with SOC
Posted: Mon Dec 05, 2022 3:25 pm
by merzuk.kaltak
Dear Sophie,
vasp-5.4.4 is symmetrizing the magnetic structure in the 010NiO_noSOC example such that you end up with a vanishing netto magnetic moment.
In vasp-6, the routines that handle symmetry have been improved and the correct magnetic moment is calculated with your input files.
I suggest to update to vasp-6 if possible.
There is a way to achieve the correct result with vasp-5.4.4 as well, but it requires to "break" the symmetry.
This means, changing the absolute value of the magnetic moments in opposite planes slightly.
For this purpose, I have re-arranged the Ni-ions in the POSCAR for easy initialization of MAGMOM as so:
Code: Select all
Ni32 O32
1.00000000000000
0.0000000000000000 0.0000000000000000 8.4411439999999995
8.4411439999999995 0.0000000000000000 0.0000000000000000
0.0000000000000000 23.4411440000000013 0.0000000000000000
Ni O
32 32
Direct
0.0000009186760082 0.0000009186760082 0.9995904741152017 !
0.2500009186760082 0.7500009186760082 0.9995904741152017 !
0.5000009186760153 0.5000009186760153 0.9995904741152017 !
0.7500009186760082 0.2500009186760082 0.9995904741152017 !
0.7499989926286190 0.9999989926286261 0.0909087713267027 !
0.9999989926286261 0.7499989926286190 0.0909087713267027 !
0.2499989926286261 0.4999989926286190 0.0909087713267027 !
0.4999989926286190 0.2499989926286261 0.0909087713267027 !
0.0000010073713739 0.5000010073713739 0.1791662286732958 !
0.5000010073713739 0.0000010073713739 0.1791662286732958 !
0.7500010073713810 0.7500010073713810 0.1791662286732958 !
0.9999990813239918 0.2499990813239918 0.2704845258847968 !
0.4999990813239918 0.7499990813239918 0.2704845258847968 !
0.2499990813239918 0.9999990813239918 0.2704845258847968 !
0.7499990813239918 0.4999990813239918 0.2704845258847968 !
0.2500010073713810 0.2500010073713810 0.1791662286732958 !
0.0000009186760082 0.5000009186760153 0.9995904741152017
0.2500009186760082 0.2500009186760082 0.9995904741152017
0.5000009186760153 0.0000009186760082 0.9995904741152017
0.7500009186760082 0.7500009186760082 0.9995904741152017
0.7499989926286190 0.4999989926286190 0.0909087713267027
0.2499989926286261 0.9999989926286261 0.0909087713267027
0.9999989926286261 0.2499989926286261 0.0909087713267027
0.4999989926286190 0.7499989926286190 0.0909087713267027
0.0000010073713739 0.0000010073713739 0.1791662286732958
0.7500010073713810 0.2500010073713810 0.1791662286732958
0.2500010073713810 0.7500010073713810 0.1791662286732958
0.5000010073713739 0.5000010073713739 0.1791662286732958
0.9999990813239918 0.7499990813239918 0.2704845258847968
0.7499990813239918 0.9999990813239918 0.2704845258847968
0.4999990813239918 0.2499990813239918 0.2704845258847968
0.2499990813239918 0.4999990813239918 0.2704845258847968
0.7500005855785261 0.0000005855785261 0.0075619336923012
0.0000005855785261 0.7500005855785261 0.0075619336923012
0.2500005855785261 0.0000005855785261 0.0075619336923012
0.7500005855785261 0.5000005855785261 0.0075619336923012
0.2500005855785261 0.5000005855785261 0.0075619336923012
0.5000005855785261 0.7500005855785261 0.0075619336923012
0.0000005855785261 0.2500005855785261 0.0075619336923012
0.5000005855785261 0.2500005855785261 0.0075619336923012
0.2499999012680476 0.2499999012680476 0.0986568337893132
0.4999999012680476 0.9999999012680476 0.0986568337893132
0.9999999012680476 0.9999999012680476 0.0986568337893132
0.4999999012680476 0.4999999012680476 0.0986568337893132
0.7499999012680476 0.7499999012680476 0.0986568337893132
0.2499999012680476 0.7499999012680476 0.0986568337893132
0.7499999012680476 0.2499999012680476 0.0986568337893132
0.9999999012680476 0.4999999012680476 0.0986568337893132
0.0000000987319524 0.2500000987319524 0.1714181662106853
0.2500000987319524 0.0000000987319524 0.1714181662106853
0.2500000987319524 0.5000000987319524 0.1714181662106853
0.5000000987319524 0.7500000987319524 0.1714181662106853
0.7500000987319524 0.0000000987319524 0.1714181662106853
0.5000000987319524 0.2500000987319524 0.1714181662106853
0.7500000987319524 0.5000000987319524 0.1714181662106853
0.0000000987319524 0.7500000987319524 0.1714181662106853
0.2499994144214739 0.2499994144214739 0.2625130663076973
0.9999994144214739 0.9999994144214739 0.2625130663076973
0.7499994144214739 0.2499994144214739 0.2625130663076973
0.9999994144214739 0.4999994144214739 0.2625130663076973
0.2499994144214739 0.7499994144214739 0.2625130663076973
0.4999994144214739 0.4999994144214739 0.2625130663076973
0.7499994144214739 0.7499994144214739 0.2625130663076973
0.4999994144214739 0.9999994144214739 0.2625130663076973
Then the positive and negative magnetic moments can be initialized like
This was enough to find following magnetic moments in the OUTCAR (gamma-only version):
Code: Select all
# of ion s p d tot
------------------------------------------
1 0.003 -0.005 -1.641 -1.644
2 0.003 -0.005 -1.641 -1.644
3 0.003 -0.005 -1.641 -1.644
4 0.003 -0.005 -1.641 -1.644
5 -0.001 -0.003 -1.606 -1.609
6 -0.001 -0.003 -1.606 -1.609
7 -0.001 -0.003 -1.606 -1.609
8 -0.001 -0.003 -1.606 -1.609
9 -0.001 -0.003 -1.606 -1.609
10 -0.001 -0.003 -1.606 -1.609
11 -0.001 -0.003 -1.606 -1.609
12 0.003 -0.005 -1.641 -1.644
13 0.003 -0.005 -1.641 -1.644
14 0.003 -0.005 -1.641 -1.644
15 0.003 -0.005 -1.641 -1.644
16 -0.001 -0.003 -1.606 -1.609
17 -0.003 0.005 1.641 1.644
18 -0.003 0.005 1.641 1.644
19 -0.003 0.005 1.641 1.644
20 -0.003 0.005 1.641 1.644
21 0.001 0.003 1.606 1.610
22 0.001 0.003 1.606 1.610
23 0.001 0.003 1.606 1.609
24 0.001 0.003 1.606 1.609
25 0.001 0.003 1.606 1.609
26 0.001 0.003 1.606 1.609
27 0.001 0.003 1.606 1.609
28 0.001 0.003 1.606 1.609
29 -0.003 0.005 1.641 1.644
30 -0.003 0.005 1.641 1.644
31 -0.003 0.005 1.641 1.644
32 -0.003 0.005 1.641 1.644
33 -0.004 -0.012 0.000 -0.015
34 -0.004 -0.012 0.000 -0.015
35 0.004 0.012 0.000 0.015
36 0.004 0.012 0.000 0.015
37 -0.004 -0.012 0.000 -0.015
38 0.004 0.012 0.000 0.015
39 0.004 0.012 0.000 0.015
40 -0.004 -0.012 0.000 -0.015
41 -0.003 0.048 0.000 0.045
42 -0.003 0.048 0.000 0.045
43 0.003 -0.048 0.000 -0.045
44 0.003 -0.048 0.000 -0.045
45 -0.003 0.048 0.000 0.045
46 0.003 -0.048 0.000 -0.045
47 0.003 -0.048 0.000 -0.045
48 -0.003 0.048 0.000 0.045
49 0.003 -0.048 0.000 -0.045
50 0.003 -0.048 0.000 -0.045
51 -0.003 0.048 0.000 0.045
52 0.003 -0.048 0.000 -0.045
53 -0.003 0.048 0.000 0.045
54 -0.003 0.048 0.000 0.045
55 0.003 -0.048 0.000 -0.045
56 -0.003 0.048 0.000 0.045
57 -0.004 -0.012 0.000 -0.015
58 0.004 0.012 0.000 0.015
59 0.004 0.012 0.000 0.015
60 -0.004 -0.012 0.000 -0.015
61 0.004 0.012 0.000 0.015
62 0.004 0.012 0.000 0.015
63 -0.004 -0.012 0.000 -0.015
64 -0.004 -0.012 0.000 -0.015
--------------------------------------------------
tot 0.000 -0.001 -0.000 -0.001
You probably can achieve similar results with the anti-symmetric initialization
by switching off symmetry using
ISYM=-1,
however, the job will probably take a long time to finish.
Re: magnetic moments in antiferromagnetic material are zero with ISPIN=2, both finite with SOC
Posted: Wed Dec 07, 2022 9:33 am
by sophie_weber
I see, thank you so much for your work and help! It's good at least to know that it was an issue with the 5.4.4 VASP, rather than a serious error in my input files. In the future I will try to use VASP 6.
Thank you again,
Sophie
Re: magnetic moments in antiferromagnetic material are zero with ISPIN=2, both finite with SOC
Posted: Mon Dec 12, 2022 4:24 pm
by merzuk.kaltak
You are welcome,
As a final remark for this thread:
vasp-5.4.4 does not symmetrize the local magnetic moments correctly (see
here).
This is a known issue which is fixed in vasp-6 only.