[Wien] total energy when using -orbc for constant V-matrix

[Hua Wu]

Many thanks for the replies and the good idea !

For my cases, the various contrained orbital states are all stable with -orbc 
(but some of them cannot be stabilized using -orb). With the converged
results using -orbc, the dmat matrix is almost the same (change of occupation 
numbers less than 5% ) as that I specified to construct the constant Vorb.
That means--the solutions came out as I wanted them to be.

thanks again --H. Wu
    
On Friday 15 May 2009 18:03, Laurence Marks wrote:
> This would add back the relevant terms, but I think there is another
> problem. There is nothing constraining your d (or f) occupancies, so
> these will vary and you may get a very inconsistent (unphysical)
> solution. You may be able to force a solution by fixing your dmat by
> hand, calculating orb with this and then running as Peter suggested
> but nothing forces the final dmat to be what you want/think it should
> be. You will have to check that the dmat in the iterations is close to
> what you wanted it to be, otherwise everything will be GIGO.
>
> On Fri, May 15, 2009 at 10:47 AM, Peter Blaha
>
> <pblaha at theochem.tuwien.ac.at> wrote:
> > Just a guess, it might work:
> >
> > Try    runsp -orb    (not -orbc !), but change the PRATT factor in
> > case.inorb to 0.0
> >
> > I expect that will run orb and the Eorb total energy contribution will
> > be added, but it will not update case.vorbup/dn.
> >
> > Please let me know if it works.
> >
> > Hua Wu schrieb:
> >> Dear Stefaan Cottenier and Laurence Marks,
> >>
> >>   Thanks a lot for your prompt replies and the useful information.
> >>
> >>  May I understand your points as follows:  The U-related part of total
> >> energy is not taken into account when using -orbc, since -orbc fixes the
> >> orbital potential and thus the calculations skip the nomal 'x -orb
> >> -up/dn' where the U-related part of total energy is calculated.
> >>
> >>  My further question is: can I regard the 'converged' total energy and
> >> forces calculated using -orbc as a quasi LDA/GGA result WITHIN the
> >> constrained orbital polarization?  If so, I may still be able to do
> >> structural relaxations using -orbc, e.g, to see (maybe roughly) how a
> >> lattice responds to the constrained orbital states (which can not be
> >> stabilized when using -orb).
> >>
> >> best regards -- H. Wu
> >>
> >> On Friday 15 May 2009 15:56, Laurence Marks wrote:
> >>> I'm fairly certain that with -orbc you are not including the
> >>> double-counting corrections which are normally calculated with x orb
> >>> -up/dn, hence large apparent changes.
> >>>
> >>> On 5/15/09, Stefaan Cottenier <Stefaan.Cottenier at ugent.be> wrote:
> >>>>  >   I tried to use LDA+U with -orbc flag to stabilize various orbital
> >>>>  > polarized states in my calculations for some transition-metal
> >>>> oxides. > In order to compare their total energies, I made a simple
> >>>> test, > namely, run 'LDA+U with -orbc' for a well converged 'LDA+U
> >>>> with -orb' > case. The total energies are expected to be the same.
> >>>> However,  it is > surprising that in my current calculations using the
> >>>> latest version, > the total energies change by several Rydbergs. I am
> >>>> wondering if any > term is missing in the calculations of the total
> >>>> energy when using > -orbc. In addition, can one use -orbc to do
> >>>> structural relaxation like > doing LDA+U with -orb ?
> >>>>
> >>>> -orbc is not meant for 'final' calculations, but rather for bringing
> >>>> the scf cycle close to a type of solution you want. Then you turn off
> >>>> -orbc (i.e. use plain -orb), after which the scf cycle will
> >>>> spontaneously stabilize in the nearest local energy minimum, which can
> >>>> (but not always should) have the qualitative properties of the
> >>>> solution you wanted to enforce.
> >>>>
> >>>>  I did notice indeed that when used that way, there are several Ry's
> >>>> of difference between energies with and without -orbc. I cannot give
> >>>> you the technical explanation for this (others ?), but never cared
> >>>> about it as I always use the energies with plain -orb anyway.
> >>>>
> >>>>  Note: -orbc freezes the orbital potential that is consistent with the
> >>>>  initial density matrices. It does not freeze the density matrices
> >>>>  themselves: they can evolve during the scf cycle. Hence, when using
> >>>>  -orbc as described above, you better check at the end of the -orbc
> >>>> scf cycle whether the final density matrices are not too different
> >>>> from your initial ones. If they are very different, you probably did
> >>>> not end up close the type of solution you wanted to enforce, and the
> >>>> subsequent -orb scf cycle might result into a selfconsistent solution
> >>>> that you do not want.
> >>>>
> >>>>
> >>>>  Stefaan
> >>>>
> >>>>
> >>>>  _______________________________________________
> >>>>  Wien mailing list
> >>>>  Wien at zeus.theochem.tuwien.ac.at
> >>>>  http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> >>
> >> _______________________________________________
> >> Wien mailing list
> >> Wien at zeus.theochem.tuwien.ac.at
> >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> >
> > --
> > -----------------------------------------
> > Peter Blaha
> > Inst. Materials Chemistry, TU Vienna
> > Getreidemarkt 9, A-1060 Vienna, Austria
> > Tel: +43-1-5880115671
> > Fax: +43-1-5880115698
> > email: pblaha at theochem.tuwien.ac.at
> > -----------------------------------------
> > _______________________________________________
> > Wien mailing list
> > Wien at zeus.theochem.tuwien.ac.at
> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien