[Wien] lda+u calculation

[Yundi Quan]

Hi,
I'm calculating NiO which is a canonical example of using LDA+U. Your
speculation is right. The non-magnetic case is the one where I started from
the converged LDA calculation. Is there a reason for that?



Yundi



On Thu, Feb 16, 2012 at 11:27 PM, Fecher, Gerhard <fecher at uni-mainz.de>wrote:

> I guess the non-magnetic solution is the one where you started from the
> converged LDA calculation
> and the magnetic one is the one where you started with LDA+U from scratch.
>
> You did not tell much about the system you are calculating and why you
> used LDA+U
> without knowing this, any thing for explanation just stays speculation.
>
> Ciao
> Gerhard
>
>
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> ________________________________________
> Von: wien-bounces at zeus.theochem.tuwien.ac.at [
> wien-bounces at zeus.theochem.tuwien.ac.at]&quot; im Auftrag von &quot;Yundi
> Quan [quanyundi at gmail.com]
> Gesendet: Freitag, 17. Februar 2012 03:34
> An: A Mailing list for WIEN2k users
> Betreff: Re: [Wien] lda+u calculation
>
> Both cases are very converged. One gives magnetic solution. The other
> gives non-magnetic solution. The magnetic solution is slightly lower in
> energy.
>
>
>
>
> On Thu, Feb 16, 2012 at 4:48 PM, Laurence Marks <L-marks at northwestern.edu
> <mailto:L-marks at northwestern.edu>> wrote:
> Maybe, or maybe not! If both cases are well converged, that means that
> for your approximations there are two locally stable spin states.
> Maybe this is real, maybe not, that is hard to say.
>
> 2012/2/16 Yundi Quan <quan at ms.physics.ucdavis.edu<mailto:
> quan at ms.physics.ucdavis.edu>>:
> > You are right. The spin state is different in two cases. Applying U
> after a
> > scf calculation seems to tend to reduce the magnetic moments.
> >
> >
> >
> >
> >
> >
> >
> >
> > On Thu, Feb 16, 2012 at 3:44 PM, Laurence Marks <
> L-marks at northwestern.edu<mailto:L-marks at northwestern.edu>>
> > wrote:
> >>
> >> If all other things are the same, the lowest energy is correct
> >> (variational principle). Probably the spin state is different in the
> >> two cases.
> >>
> >> But...please ensure that you really have both converged. Assuming that
> >> you have a recent version, do a "grep -e :MV case.scf" (with case
> >> replaced as appropriate). The % value should be small for true
> >> convergence; if it is not you do not have real convergence
> >> (technically it is called a "trap").
> >>
> >> 2012/2/16 Yundi Quan <quanyundi at gmail.com<mailto:quanyundi at gmail.com>>:
> >> > Dear Sir/Madam,
> >> > When using LSDA+U, it is recommended to first do an LSDA caculation
> and
> >> > then
> >> > turn on U. I first did an LSDA calculation to convergence. Then, I
> >> > turned on
> >> > U. I also did a calculation by turning on U from the very beginning. I
> >> > compared the two results, and found that the later is lower in energy.
> >> > Which
> >> > one is correct?
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > _______________________________________________
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> >> > Wien at zeus.theochem.tuwien.ac.at<mailto:
> Wien at zeus.theochem.tuwien.ac.at>
> >> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> >> >
> >>
> >>
> >>
> >> --
> >> Professor Laurence Marks
> >> Department of Materials Science and Engineering
> >> Northwestern University
> >> www.numis.northwestern.edu<http://www.numis.northwestern.edu>
> 1-847-491-3996<tel:1-847-491-3996>
> >> "Research is to see what everybody else has seen, and to think what
> >> nobody else has thought"
> >> Albert Szent-Gyorgi
> >> _______________________________________________
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> >
> >
> >
> > _______________________________________________
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> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> >
>
>
>
> --
> Professor Laurence Marks
> Department of Materials Science and Engineering
> Northwestern University
> www.numis.northwestern.edu<http://www.numis.northwestern.edu>
> 1-847-491-3996<tel:1-847-491-3996>
> "Research is to see what everybody else has seen, and to think what
> nobody else has thought"
> Albert Szent-Gyorgi
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at<mailto:Wien at zeus.theochem.tuwien.ac.at>
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
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