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).
Yours sincerely, Hung-Yu On Mon, Aug 7, 2017 at 4:27 AM, pieper <pie...@ifp.tuwien.ac.at> wrote: > 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. > > --- > Dr. Martin Pieper > Karl-Franzens University > Institute of Physics > Universitätsplatz 5 > A-8010 Graz > Austria > Tel.: +43-(0)316-380-8564 > > > Am 07.08.2017 09:18, schrieb Peter Blaha: > >> The Ir moments are read from case.scf file, but why should it be near >>> an integer, and what is the unit of the reported moments in case.scf >>> file? If the unit is bohr magneton, then for a spin 1/2, should it be >>> ~1.7? >>> >> >> For a FERROmagnetic insulator, the TOTAL spin moment/cell must be >> integer. The moments of individual atoms can have any value. >> >> For an ANTIferromagnet, the total spin moment/cell must be zero, and >> of course the atomic moments can again have any value. >> >> What you get by :MMT or MMIxxx are spin moments only. >> >> The moments are given in Bohr magnetons (mu_B), but are the spin >> moments, not the effective moments. Thus if you have one unpaired >> electron the spin moment is one. >> >> PS: For your compound, the orbital moments are probably as important >> as the spin moments and you must add them to get the total moment. >> >> >> >> >>> The gap can be roughly seen along the k-path I plotted and is checked by >>> DOS plot, which shows it's an insulator. >>> >>> Yours sincerely, >>> >>> Hung-Yu >>> >>> On Sun, Aug 6, 2017 at 11:03 AM, pieper <pie...@ifp.tuwien.ac.at >>> <mailto:pie...@ifp.tuwien.ac.at>> wrote: >>> >>> A few thoughts on this: >>> >>> ad 1) >>> Presumably Ir is the magnetic ion, so what you describe seems to be >>> ok with me. I did not check your .struct file, however. >>> >>> ad 2) >>> See chapters 4.5.6 and 7.4 of the UG (Wien2k 17.1) on ther >>> orb-program, and the references therein. Personally I found the .pdf >>> file of his talk on LDA+U very usefull that E. Assmann posted on the >>> Wien2k-site. >>> >>> Note the recommendation in the UG for the SIC-mode of orb for of >>> strongly correlated systems: set J=0 and use only U_eff=U-J. The >>> value of U_eff is something you will have to decide, perhaps based >>> on the approach described by Madsen and Novak cited in the UG. You >>> also might want to take a look at eece as an alternative (UG chapter >>> 4.5.7) >>> >>> >From many comments here in the mailing list and from the UG (again >>> e.g. chapter 5.5.7, 4.5.8) I take it that PBE is what you should do >>> if you want to calculate spacial charge and spin distributions, but >>> to calculate gaps you may have to switch to numerically much more >>> costly hybrid methods. >>> >>> You probably can (mis)use U_eff as a free parameter to adjust the >>> gap in your PBE calculation to your favorite value. However, the >>> physical meaning of the value would be dubious (imho), and there is >>> no guarantee that the Ir-moments simultaneously come near your >>> favorit 'theoretical moments' (whatever the actual value and origin >>> of those is). >>> >>> ad 3) Don't bother with the starting values of local moments for >>> atomic configurations, and for an antiferromagnet the interstitial >>> moment obviously should stay close to zero. >>> >>> But the moments you give in your table are very far from integer. >>> Are this Ir-spin moments from case.scf or did you add orbital >>> moemnts calculated by lapwdm? The spin moments should be somewhere >>> near integer for an insulator. >>> >>> So, how did you determine the gap in the table? Did you plot a DOS? >>> Is this really an insulator, or are there in fact bands crossing >>> E_F? You might severly misjudge the (direct?) gap depending on where >>> in k-space it is and the points in your k-list. >>> >>> Good luck >>> >>> --- >>> Dr. Martin Pieper >>> Karl-Franzens University >>> Institute of Physics >>> Universitätsplatz 5 >>> A-8010 Graz >>> Austria >>> Tel.: +43-(0)316-380-8564 <tel:%2B43-%280%29316-380-8564> >>> >>> >>> >>> Am 04.08.2017 19:22, schrieb 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 >>> _______________________________________________ >>> Wien mailing list >>> Wien@zeus.theochem.tuwien.ac.at >>> <mailto:Wien@zeus.theochem.tuwien.ac.at> >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >>> <http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien> >>> SEARCH the MAILING-LIST at: >>> http://firstname.lastname@example.org/ >>> index.html >>> <http://email@example.com >>> /index.html> >>> >>> _______________________________________________ >>> Wien mailing list >>> Wien@zeus.theochem.tuwien.ac.at <mailto:w...@zeus.theochem.tuw >>> ien.ac.at> >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >>> <http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien> >>> SEARCH the MAILING-LIST at: >>> http://firstname.lastname@example.org/ >>> index.html >>> <http://email@example.com >>> /index.html> >>> >>> >>> >>> >>> _______________________________________________ >>> Wien mailing list >>> Wien@zeus.theochem.tuwien.ac.at >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >>> SEARCH the MAILING-LIST at: http://www.mail-archive.com/wi >>> e...@zeus.theochem.tuwien.ac.at/index.html >>> >>> _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: http://www.mail-archive.com/wi > e...@zeus.theochem.tuwien.ac.at/index.html >
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