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 ? 13:36, Davide Tiana a ?crit : > >>> > >>>> > >>>> 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 > >>> > >>> > >>> _______________________________________________ > >>> Pw_forum mailing list > >>> Pw_forum at pwscf.org > >>> http://pwscf.org/mailman/listinfo/pw_forum > >> > >> _______________________________________________ > >> Pw_forum mailing list > >> Pw_forum at pwscf.org > >> http://pwscf.org/mailman/listinfo/pw_forum > > > > -- > > Paolo Giannozzi, Dept. Chemistry&Physics&Environment, > > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > > Phone +39-0432-558216, fax +39-0432-558222 > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://pwscf.org/mailman/listinfo/pw_forum > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20140425/4b681358/attachment.html
