<div dir="ltr">Thanks a lot for the replies from both of you! And in this case the orbital moment is indeed not negligible when I checked :ORB (~0.4).<div><br></div><div>Yours sincerely,</div><div><br></div><div>Hung-Yu</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Aug 7, 2017 at 4:27 AM, pieper <span dir="ltr"><<a href="mailto:pieper@ifp.tuwien.ac.at" target="_blank">pieper@ifp.tuwien.ac.at</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Of course! The local moments in an AF insulator can be anything. I just saw that there is only one type of magnetic atom in the unit cell (Ir) and did not think properly. Sorry for that one.<span class="im HOEnZb"><br>
<br>
---<br>
Dr. Martin Pieper<br>
Karl-Franzens University<br>
Institute of Physics<br>
Universitätsplatz 5<br>
A-8010 Graz<br>
Austria<br>
Tel.: <a href="tel:%2B43-%280%29316-380-8564" value="+433163808564" target="_blank">+43-(0)316-380-8564</a><br>
<br>
<br></span><div class="HOEnZb"><div class="h5">
Am 07.08.2017 09:18, schrieb Peter Blaha:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
The Ir moments are read from case.scf file, but why should it be near<br>
an integer, and what is the unit of the reported moments in case.scf<br>
file? If the unit is bohr magneton, then for a spin 1/2, should it be ~1.7?<br>
</blockquote>
<br>
For a FERROmagnetic insulator, the TOTAL spin moment/cell must be<br>
integer. The moments of individual atoms can have any value.<br>
<br>
For an ANTIferromagnet, the total spin moment/cell must be zero, and<br>
of course the atomic moments can again have any value.<br>
<br>
What you get by :MMT or MMIxxx are spin moments only.<br>
<br>
The moments are given in Bohr magnetons (mu_B), but are the spin<br>
moments, not the effective moments. Thus if you have one unpaired<br>
electron the spin moment is one.<br>
<br>
PS: For your compound, the orbital moments are probably as important<br>
as the spin moments and you must add them to get the total moment.<br>
<br>
<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
The gap can be roughly seen along the k-path I plotted and is checked by<br>
DOS plot, which shows it's an insulator.<br>
<br>
Yours sincerely,<br>
<br>
Hung-Yu<br>
<br>
On Sun, Aug 6, 2017 at 11:03 AM, pieper <<a href="mailto:pieper@ifp.tuwien.ac.at" target="_blank">pieper@ifp.tuwien.ac.at</a><br>
<mailto:<a href="mailto:pieper@ifp.tuwien.ac.at" target="_blank">pieper@ifp.tuwien.ac.a<wbr>t</a>>> wrote:<br>
<br>
A few thoughts on this:<br>
<br>
ad 1)<br>
Presumably Ir is the magnetic ion, so what you describe seems to be<br>
ok with me. I did not check your .struct file, however.<br>
<br>
ad 2)<br>
See chapters 4.5.6 and 7.4 of the UG (Wien2k 17.1) on ther<br>
orb-program, and the references therein. Personally I found the .pdf<br>
file of his talk on LDA+U very usefull that E. Assmann posted on the<br>
Wien2k-site.<br>
<br>
Note the recommendation in the UG for the SIC-mode of orb for of<br>
strongly correlated systems: set J=0 and use only U_eff=U-J. The<br>
value of U_eff is something you will have to decide, perhaps based<br>
on the approach described by Madsen and Novak cited in the UG. You<br>
also might want to take a look at eece as an alternative (UG chapter<br>
4.5.7)<br>
<br>
>From many comments here in the mailing list and from the UG (again<br>
e.g. chapter 5.5.7, 4.5.8) I take it that PBE is what you should do<br>
if you want to calculate spacial charge and spin distributions, but<br>
to calculate gaps you may have to switch to numerically much more<br>
costly hybrid methods.<br>
<br>
You probably can (mis)use U_eff as a free parameter to adjust the<br>
gap in your PBE calculation to your favorite value. However, the<br>
physical meaning of the value would be dubious (imho), and there is<br>
no guarantee that the Ir-moments simultaneously come near your<br>
favorit 'theoretical moments' (whatever the actual value and origin<br>
of those is).<br>
<br>
ad 3) Don't bother with the starting values of local moments for<br>
atomic configurations, and for an antiferromagnet the interstitial<br>
moment obviously should stay close to zero.<br>
<br>
But the moments you give in your table are very far from integer.<br>
Are this Ir-spin moments from case.scf or did you add orbital<br>
moemnts calculated by lapwdm? The spin moments should be somewhere<br>
near integer for an insulator.<br>
<br>
So, how did you determine the gap in the table? Did you plot a DOS?<br>
Is this really an insulator, or are there in fact bands crossing<br>
E_F? You might severly misjudge the (direct?) gap depending on where<br>
in k-space it is and the points in your k-list.<br>
<br>
Good luck<br>
<br>
---<br>
Dr. Martin Pieper<br>
Karl-Franzens University<br>
Institute of Physics<br>
Universitätsplatz 5<br>
A-8010 Graz<br>
Austria<br>
Tel.: <a href="tel:%2B43-%280%29316-380-8564" value="+433163808564" target="_blank">+43-(0)316-380-8564</a> <tel:%2B43-%280%29316-380-8564<wbr>><br>
<br>
<br>
<br>
Am 04.08.2017 19:22, schrieb Hung Yu Yang:<br>
<br>
Dear WIEN2k developers and users,<br>
<br>
I am trying to do a calculation on Na2IrO3, which has a band gap<br>
~340meV and a zigzag antiferromagnetic order in its ground<br>
state, and<br>
I have some questions as follow:<br>
<br>
1. To assign the zigzag antiferromagnetic order, what I did is<br>
that I<br>
first made a cif file that has two inequivalent Ir atoms, and let<br>
WIEN2k decide the symmetry for me. I adopted the generated<br>
structural<br>
file (attached in this mail), checked the cif file in some<br>
visulization software and made sure they were structurally<br>
equivalent<br>
except that there were 2 inequivalent Ir atoms instead of 1. Is this<br>
the proper way to generate structural files for magnetically ordered<br>
systems?<br>
<br>
2. After generating the desired structural file, I put up on Ir1<br>
atom<br>
and down on the other (Ir2), used several different combinations<br>
of U<br>
and J, and I got the following results:<br>
<br>
U(eV) J(eV) Ueff=U-J (eV) Moment(Ir1, Ir2)<br>
Gap(meV)<br>
2.1 0.6 1.5<br>
0.22532,-0.22439 ~700meV<br>
2.4 0 2.4<br>
0.30105,-0.30109 ~750meV<br>
3 0.6 2.4<br>
0.23225,-0.23235 ~900meV<br>
3 1.5 1.5<br>
0.17203,-0.17210 ~900meV<br>
<br>
First, in this test, it seems that the gap is affected by U<br>
only, not<br>
Ueff=U-J. Second, the moments of Ir seemed to be closely related<br>
to J.<br>
In this situation, what is the proper way to assign U and J? I<br>
am not<br>
sure how much it means if I just try to tune U and J until they<br>
match<br>
the experimental gap and/or theoretical moments.<br>
<br>
3. I also have a question about the unit of moment given here; I<br>
understand that the moments depend on the RMT sizes and I<br>
assumed the<br>
unit is in bohr magneton, but the first value shown for Ir atom is<br>
0.76697 and I am not sure in what unit is this value and how it<br>
assigns the initial moment for a certain element (say, Ir in my<br>
case).<br>
Also, the interstitial moments are nearly 0 among all the cycles.<br>
<br>
For this calculation, kpoints=450, RKmax=8 and I had to use the TEMP<br>
scheme for it to converge. I appreciate any reply from you.<br>
<br>
Yours sincerely,<br>
<br>
Hung-Yu<br>
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