System gives wrong magnetic moment for soc, but giving correct moment for...
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Dear elkers,
I am doing the scf calculations for YFeO3, with and without spin-orbital coupling.
When running the calculations without spin-orbital coupling, the system get converged, giving reasonable results (e.g., magnetic moments look fine, see below).
However, when switching on the SOC, the calculation is difficult to converge, and the output magnetic moments are quite wrong (e.g., very tiny, see below).
Could anyone please help me with this issue? Thanks a lot.
PS: I attached my input files.
____Calculations without SOC_____
RMS change in Kohn-Sham potential (target) : 0.1357496288E-06 ( 0.1000000000E-05)
Absolute change in total energy (target) : 0.9344737919E-05 ( 0.1000000000E-03)
Convergence targets achieved
Moments :
interstitial : 0.1333162598E-15
muffin-tins
species : 1 (Y)
atom 1 : -0.1160391484E-21
atom 2 : -0.1160391484E-21
atom 3 : 0.1160391484E-21
atom 4 : -0.1160391484E-21
species : 2 (Fe)
atom 1 : -3.529474466
atom 2 : 3.529474466
atom 3 : 3.529474466
atom 4 : -3.529474466
species : 3 (O)
atom 1 : -0.1329639896E-01
atom 2 : -0.1329639896E-01
atom 3 : 0.1329639896E-01
atom 4 : 0.1329639896E-01
atom 5 : 0.1329639896E-01
atom 6 : 0.1329639896E-01
atom 7 : -0.1329639896E-01
atom 8 : -0.1329639896E-01
atom 9 : -0.2836435592E-21
atom 10 : -0.2836435592E-21
atom 11 : 0.2836435592E-21
atom 12 : -0.2836435592E-21
total in muffin-tins : -0.4440897771E-15
total moment : -0.3107735173E-15
_____Calculations with SOC___
RMS change in Kohn-Sham potential (target) : 0.1713924931E-04 ( 0.1000000000E-05)
Absolute change in total energy (target) : 0.1640330920E-02 ( 0.1000000000E-03)
Time (CPU seconds) : 15943.04
+--------------------+
| Loop number : 200 |
+--------------------+
Moments :
interstitial : 0.8673650164E-02 0.3142857646E-09 0.1898490302E-09
muffin-tins
species : 1 (Y)
atom 1 : 0.5673422695E-03 -0.1588477447E-02 -0.1539704381E-03
atom 2 : 0.5673422695E-03 -0.1588477447E-02 -0.1539704381E-03
atom 3 : 0.5673422695E-03 0.1588477447E-02 0.1539704381E-03
atom 4 : 0.5673422695E-03 0.1588477447E-02 0.1539704381E-03
species : 2 (Fe)
atom 1 : 0.5583798361E-01 -0.9705815563E-01 -0.1533894636
atom 2 : 0.5583798361E-01 0.9705815563E-01 0.1533894636
atom 3 : 0.4031345523E-01 -0.9284744163E-01 0.1641584198
atom 4 : 0.4031345523E-01 0.9284744163E-01 -0.1641584198
species : 3 (O)
atom 1 : -0.7392675071E-02 -0.3564528400E-02 0.3589331188E-02
atom 2 : -0.7392675071E-02 -0.3564528400E-02 0.3589331188E-02
atom 3 : -0.7392675071E-02 0.3564528400E-02 -0.3589331188E-02
atom 4 : -0.7392675071E-02 0.3564528400E-02 -0.3589331188E-02
atom 5 : -0.9854364448E-02 -0.8611391621E-02 -0.4885946100E-02
atom 6 : -0.9854364448E-02 -0.8611391621E-02 -0.4885946100E-02
atom 7 : -0.9854364448E-02 0.8611391621E-02 0.4885946100E-02
atom 8 : -0.9854364448E-02 0.8611391621E-02 0.4885946100E-02
atom 9 : -0.1964584570E-01 0.4897128955E-02 -0.1882306375E-03
atom 10 : -0.1964584570E-01 0.4897128955E-02 -0.1882306375E-03
atom 11 : -0.1964584570E-01 -0.4897128955E-02 0.1882306375E-03
atom 12 : -0.1964584570E-01 -0.4897128955E-02 0.1882306375E-03
total in muffin-tins : 0.4700070587E-01 -0.3989863995E-16 -0.2775557562E-16
total moment : 0.5567435603E-01 0.3142857247E-09 0.1898490025E-09
Dear Zhao,
I would first check if you need a dft+u calculation here. Is this system an insulator? How large is the DFT-noSC gap. If it is an insulator and the gap is already small, it might be closed by the LS-coupling and then it will be hard to find the insulating AFM solution.
If this is not the case, I would suggest checking to start with larger fields instead of 0.01 maybe start with 1 and set
reducebf
0.9
so the field is kept longer on. This might help to achieve convergence of the AFM state.
hope this helps
best wishes
michael
Dear Michael,
Thanks a lot! This system has a gap and a magnetic moment of ~ 4 uB on Fe site. By LSDA+U calculation (no soc), the magnetic moment is basically reproduced, while the gap is underestimated (not bad). During the soc calculations, I tried to increase the initial magnetic field to 1 and set reducebf=0.9; The calculations still cannot be converged to a correct magnetic moment (magnetic moment being ~ 0.6 uB/Fe).
Are there any other solutions to "guide" the soc calculation find the correct solution? Thanks a lot.
Best wishes,
HJ
Dear Zhao,
could you try linear mixing instead so set
mixtype
1
and then reduce the mixing
betamax
0.3
best
michael
Thanks a lot. I tried with your proposed mixing type and betamax; The calculations still converge to a state with wrong magnetic moment (e.g., similar to that from the previous calculations).
Does the Muffin tin radius matter, regarding the spin for noncollinear? Thanks a lot.
Okay Zhao,
I played around with your input cards and came to the following conclusions:
There exist two magnetic states which elk can converge in the case of no-ls coupling. These are a high spin state (4+ mub on Fe) and another low spin state (1 mub on Fe). This depends a little bit on the U you apply. Increasing your U always induced the second state.
I think now once you switch on LS coupling you may modify the bands structure and hence the low spin state becomes favored, which moment even becomes quenched somehow.
Consequently, I would suggest you to carefully scan the U-values in hte spin-orbit case to check if for lower U the high spin state becomes stable again.
best wishes
Michael
Thanks a lot. When removing the Hubbard U values, it indeed works. The calculations seem to converge to a reasonable magnetic moment. I will test the Hubbard U. Thanks again for your nice suggestions.
Best wishes,
Hongjian