[Wien] Questions about Na2IrO3 (PBE+SOC+U calculation with magnetic order)

[Hung Yu Yang]

Dear WIEN2k developers and users,

I am trying to do a calculation on Na2IrO3, which has a band gap ~340meV
and a zigzag antiferromagnetic order in its ground state, and I have some
questions as follow:

1. To assign the zigzag antiferromagnetic order, what I did is that I first
made a cif file that has two inequivalent Ir atoms, and let WIEN2k decide
the symmetry for me. I adopted the generated structural file (attached in
this mail), checked the cif file in some visulization software and made
sure they were structurally equivalent except that there were 2
inequivalent Ir atoms instead of 1. Is this the proper way to generate
structural files for magnetically ordered systems?

2. After generating the desired structural file, I put up on Ir1 atom and
down on the other (Ir2), used several different combinations of U and J,
and I got the following results:

U(eV)         J(eV)         Ueff=U-J (eV)      Moment(Ir1, Ir2)
 Gap(meV)
2.1             0.6             1.5                       0.22532,-0.22439
       ~700meV
2.4             0                2.4                       0.30105,-0.30109
       ~750meV
3                0.6             2.4                       0.23225,-0.23235
       ~900meV
3                1.5             1.5                       0.17203,-0.17210
       ~900meV

First, in this test, it seems that the gap is affected by U only, not
Ueff=U-J. Second, the moments of Ir seemed to be closely related to J. In
this situation, what is the proper way to assign U and J? I am not sure how
much it means if I just try to tune U and J until they match the
experimental gap and/or theoretical moments.

3. I also have a question about the unit of moment given here; I understand
that the moments depend on the RMT sizes and I assumed the unit is in bohr
magneton, but the first value shown for Ir atom is 0.76697 and I am not
sure in what unit is this value and how it assigns the initial moment for a
certain element (say, Ir in my case). Also, the interstitial moments are
nearly 0 among all the cycles.

For this calculation, kpoints=450, RKmax=8 and I had to use the TEMP scheme
for it to converge. I appreciate any reply from you.

Yours sincerely,

Hung-Yu
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