I do NOT officially support 2 l values / atom for GGA+U. It may/may not
work in various programs.
The reason is simply, that in WIEN2k the U is applied only inside the
sphere and the V_orb potential is calculated from the occupations of an
orbital, varying from 0 to 1.
I.e. if n=1 (an orbital is fully occupied), it gets a potential which
shifts this state by U/2 down, on the other hand, if a particular
orbital is empty, it will be shifted up by U/2.
The problems come with relatively "delocalized" orbitals like the 5d
states of a 4f element.
Check out the "fractional charge" within the sphere as printed in
case.outputst.
4F* -0.590624 -0.590624 2.50 2.50 0.9844 F
5D* -0.208649 -0.208649 0.50 0.50 0.4864 F
You can find that Sm-4f is nearly completely confined in the sphere
(0.9844) and applicationsof U is "well defined", but one 5d electron has
less than 0.5 e inside the sphere !!!
Depending on the rare earth and on RMT it means that even a fully
occupied 5d state does NOT get shifted down due to GGA+U, but basically
all d-orbitals will be shifted up.
Am 24.07.2020 um 18:03 schrieb pluto:
Dear All,
I am trying to calculate a simple 4f compound with GGA+U, ferromagnetic
exchange (FM) and SOC. FM calculation without SOC using the literature U
settings looks reasonable, I am getting a gapped band structure similar
to anyone else.
But running SCF with GGA+U and SOC removes the gap, it also seems to
change the exchange splitting of 4f, which basically tells me that U on
4f is not in effect anymore. Actually the problem happens with this
inorb file, when natorb=1 and nlorb=2:
1 1 0 nmod, natorb, ipr
PRATT 1.0 BROYD/PRATT, mixing
1 2 2 3 iatom nlorb, lorb
1 nsic 0..AMF, 1..SIC, 2..HFM
0.25 0.00 U J U on d levels
0.42 0.00 U J U on f levels
When nlorb is reduced to 1, and U is used only for 4f levels things
start to look "normal" also with SOC. So, it seems SOC cannot handle
nlorb>1 (perhaps just a bug).
I am using couple of years old version of WIEN2k, perhaps this has been
fixed in the meantime. Otherwise, any comment would be appreciated!
Best,
Lukasz
--
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at
WWW:
http://www.imc.tuwien.ac.at/tc_blaha-------------------------------------------------------------------------
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