[Pw_forum] tpss: too many bands are not converged

Sat Apr 26 02:06:15 CEST 2014

Dear Davide,
Last 2-3 days, I also trying to run some Meta GGA calculations with TPSS
functional (Very small molecule, like NH3, CH4).
When the box length was less than 10 angstrom, its works, at least I dont
face the convergence failure problem.
When I increase the box length(15-20 angstrom) i got the similar kind of
error with QE-5.0.3 version.
But its work for QE-4.2.1 version.  May be you can try it with QE-4.2.1 .
I dont understand, why the QE-5.0.0 to QE-5.0.3 or trunk version is not
working.
Probable thay have changes something in the new Meta GGA code.
Thanks
Ananya

On Fri, Apr 25, 2014 at 9:10 AM, Mike Marchywka <marchywka at hotmail.com>wrote:

>
>
>
>
>
> ----------------------------------------
> > From: paolo.giannozzi at uniud.it
> > To: pw_forum at pwscf.org
> > Date: Fri, 25 Apr 2014 03:42:06 +0200
> > Subject: Re: [Pw_forum] tpss: too many bands are not converged
> >
> > On Thu, 2014-04-24 at 09:03 -0400, Mike Marchywka wrote:
> >
> >> By free volume, you mean places where n and likely grad everything are
> numerical noise?
> >
> > exactly: the regions of space where the charge has decayed to noise.
> > Apparently (the current implementation of) meta-GGA doesn't like the
> > presence of such large regions (and it doesn't seem to like H atoms
> > as well). Even plain GGA diverges in those regions: it is less of a
> > problem, but still, the exact energy values depend upon how the
>
> Does it actually diverge or just reach some kind of limit cycle with
> amplitude in energy greater than convergence criteria?
>
> > potential is cut off. The divergence comes from gradient corrections
> > to exchange: there is no divergence in atoms with the correct large-r
>
> so this is related to PP and lack of exponential decay giving more weight
> to "free volume" than it should physically have? I had been doing some
> tests with analytical hydrogen since it was easy to check :) That is not
> noise
> alone then but a modelling issue.
>
> > limit of the charge density, but this is not of much help in plane-wave
> > calculations of condensed-matter systems.
>
> Molecular crystals better or worse than say metals?
>
> >From what I can tell of the TPSS "z" anyway, trying to calculate it
> as a ratio of intermediate real quantities seems to allow for many errors
> such as aliasing that may occur by taking magnitudes.  I did some
> algebra it looks like the magnitude of the grad of the wf angle is more
> direct but I have
> not checked the math or tested it much although IIRC some related results
> vs analytical hydrogen did not appear obviously wrong but this was hardly
> a complete test.
>
>
>
> >
> > (disclaimer: this is what I remember. I looked at this problem several
> > years ago for meta-GGA, many years ago for GGA)
>
>
> Thanks, I'm just trying to understand a few things and see if I can play
> with
> the problematic terms and evaluate some alternatives.
>
> >
> > Paolo
> >> AFAICT, the converge of SCF is largely empirical
> >> as there does not seem to be much theory here. In any case, you would
> like to think that the areas lacking "physics" should not be that
> >> big a factor in the overall calculation and if that is not the case
> there may be something interesting here to explore :)
> >>
> >>> You can try to decrease the size of the unit-cell in order to minimize
> the free space it contains. Of course, this will be at the expense of the
> inter-polyemer interaction you probably want to avoid.
> >>>
> >>> Nevertheless, this will probably not cure your problem, which to my
> knowledge has no other solution than changing the meta-GGA functional to a
> GGA one.
> >>
> >> I took a look at the "z" parameter which being a ratio could have some
> issue with small denominators. With some initial work,
> >> it looks like there are better ways to calculate it than directly from
> real quantities such as n and grad mags,
> >> but I am still trying to test what may be trivially wrong math :)
> >> I think my latest result was something to the effect that you could
> reduce z to A/(A+B)( both non-negative)
> >> if you calculate everything from psi and the grad of psi expressed in
> polar form, not much different from some formula
> >> for current densities, and maybe find a limit when A and B are both
> zero.
> >>
> >> I had originally hoped to try to test it for trivial issues in JDFTX
> and c++ or c with libxc using an expanded interface scheme
> >> to let me pass z or grad psi in polar form but it will require a bit of
> effort. Curious if anyone else here has examined
> >> this or has literature references they care to share. Seems
> disconcerting that something with physical meaning would have these
> >> kinds of implementation issues - perhaps something else can be learned
> from investigating.
> >>
> >> Thanks.
> >>
> >>> Best regards,
> >>>
> >>> Yves
> >>>
> >>>
> >>>
> >>> Le 24 avr. 2014 à 13:36, Davide Tiana a écrit :
> >>>
> >>>>
> >>>> Dear all,
> >>>> I've been trying to calculate a polymer using tpss. I already fully
> >>>> optimised it with different functional (pbesol, pw91, hse) and
> >>>> pseudopotential (nc, paw). For some reason (apologise my ignorance if
> >>>> it should be well known) when I try to calculate using tpss nc the
> >>>> system simply does not converge crashing with this error:
> >>>>
> >>>> Error in routine c_bands (1):
> >>>> too many bands are not converged
> >>>>
> >>>> After some reaserch in old pw-forum mails, I tried decreasing
> >>>> mixing_beta=0.2, increasing mixing_ndim=12, as well as mixing mode TF
> >>>> and local-TF.
> >>>> everythings failed.
> >>>>
> >>>> Does anyone have any tips or idea of why the system can't converge?
> >>>>
> >>>> Thanks a lot,
> >>>> Davide
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> Pw_forum mailing list
> >>>> Pw_forum at pwscf.org
> >>>> http://pwscf.org/mailman/listinfo/pw_forum
> >>>
> >>>
> >>> _______________________________________________
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> >>
> >> _______________________________________________
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> >
> > --
> > Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> > Phone +39-0432-558216, fax +39-0432-558222
> >
> > _______________________________________________
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