[Wien] Charge convergence

[Luis Ogando]

Dear Prof. Marks,

   Thank you very much for your explanation.
   Unfortunatelly, I am stil using Wien2k 14.2, without the "Check" command.
   Anyway, I can wait for the charge convergence (for a while). If it takes
too long and nothing bad happens, I will "kill" the optimization.
   Thank you again.
                All the best,
                             Luis


2017-07-11 13:13 GMT-03:00 Laurence Marks <L-marks at northwestern.edu>:

> It is possible for :ENE (Energy, -ec) to seem to converge, but has not
> -- so it is always wise IMO to also use the charge converge (:DIS,
> -cc). A value of .0004130 is probably OK, I suggest using the "Check"
> command which gives more information. (Peter added it to version 16,
> presumably 17 as well as a command Check-mixing.)
>
> From the variational principle, the density converges more slowly than
> the energy. Depending upon what you are trying to do your charge
> convergence may be fine. For something like phonons it probably is
> not. I will note that very good charge convergence often requires good
> k-mesh, RKMAX etc, more than is needed for a routine calculation.
>
> N.B., with more atoms charge convergence can be harder to achieve --
> and less important.
>
> On Tue, Jul 11, 2017 at 9:40 AM, Luis Ogando <lcodacal at gmail.com> wrote:
> > Dear Prof. Marks and Wien2k community,
> >
> >    Good afternoon !
> >    Just a curiosity about the charge convergence criteria. I am
> optimizing a
> > supercell and the charge convergence limit I am using is 0.001. The same
> > numerical value for the energy convergence.
> >    The energy is finally converged, but the charge is not despite the
> fact
> > that its change is below the limit in the last 10 iterations.
> >
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  1 0.001 -.0002028
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  0 0.001 .0006007
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  1 0.001 -.0002590
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  0 0.001 .0007240
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  0 0.001 .0008640
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  0 0.001 .0005344
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  0 0.001 .0005217
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  0 0.001 .0002525
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  0 0.001 .0004560
> > CarbazoleLDAopt.dayfile::CHARGE convergence:  0 0.001 .0004130
> >
> >    If I am not wrong, the convergence is achieved after 3 consecutive
> > iterations with changes below the limit, but in my case this is happening
> > for more than 10 iterations  without convergence.
> >    Could you please kindly explain what may be happening ?
> >    Thank you !
> >                     Luis
> >
>
>
>
> --
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what
> nobody else has thought", Albert Szent-Gyorgi
> www.numis.northwestern.edu ; Corrosion in 4D:
> MURI4D.numis.northwestern.edu
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> Co-Editor, Acta Cryst A
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