Igor, Thanks for the suggestion. For the compound I am faced with, Ce127, I treated 4f as localized states first by following the instruction given in WIEN2k-FAQ: "open core" treatment of 4(5)f electrons
and the procedure worked fine. But I also noticed the comment "A better approach would be to use LDA+U, which is available in WIEN2k." I then had to fight with the whole business of the convergence problem. As for Ce in the compound being mixed valence state or not, how can we decide a priori? The conventional LDA calculation always puts the Ce 4f close to the Fermi energy, yielding a fractional occupation. I appreciate if you can share more of your experience. You are right. The LDA+U to iron pnictides is unphysical because they are metallic. I simply used it to find out why the LDA+U does not work for Ce systems. Laurence, I just copied the two files you pointed from 10.1 into 9.2 SRC_mixer folder, and will report again what I can obtain. Best regards, Jianxin On Aug 3, 2010, at 8:52 AM, mazin wrote: > Laurence, > > Thanks for your comments. It is a good idea to download a newer > version anyway, but unfortunately my problem is of different sort. I > can converged to the machine accuracy both calculations, WIEN2k_07 > and WIEN2k_09, and the results are physically different. I have no > problem with convergence in either case, and can verify manually > that both calculations are fully converged. The problem is therefore > unrelated to a possible bug in the mixing scheme. > > Jianxin, > Ce in some compounds is in mixed valence state or close to that. In > those cases, you may have problems with convergence, and you should > be careful fighting these problems, because even if you manage to > converge the calculations, that may be a rather unphysical solution. > In CeTe3 Ce is not close to mixed valency so there is no problem > with convergence. Neither should there be any with pnictides, > assuming you are talking about U on Fe, except that LDA+U is > completely unphysical for these materials. > > Igor > -- > ********************************************************************** > Igor Mazin, NRL, code 6390, 4555 Overlook Ave SW, Washington, DC 20375 > Phone: (202) 767-6990; Fax: (202) 404-7546; e-mail mazin at nrl.navy.mil > Home Page http://cst-www.nrl.navy.mil/users/mazin > ********************************************************************** > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20100803/22f21001/attachment.htm>