[Pw_forum] Non Convergence

[BARRETEAU Cyrille]

The value of nbnd is particularly important for magnetic system since in priniciple one should have a larger nbnd for majority bands than for minority bands.  We found that a safer value is nelec/2*1.5
In some cases it can really lead to convergence problem, for slabs or clusters..
Cyrille


________________________________________
De : pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] de la part de Paolo Giannozzi [paolo.giannozzi at uniud.it]
Envoyé : jeudi 6 novembre 2014 18:47
À : PWSCF Forum
Objet : Re: [Pw_forum] Non Convergence

On Thu, 2014-11-06 at 17:12 +0000, BARRETEAU Cyrille wrote:

> I would also advise to increase nbnd since for magnetic system
> the default value is often too small. I usually take nbnd=nelec/2*1.5
> instead of the default value of nelec/2*1.2
>
> Therefore you should take at least nbnd=80 instead of 60.

the original input had a larger nbnd. I reduced it just to speed up the
calculation. I agree that it is on the lower bounds of what one can
safely use with metals.

Paolo

> Cyrille
> --------------------------------------------------------------------------
> Cyrille Barreteau
> CEA Saclay, IRAMIS, SPEC Bat. 771
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>
> ________________________________________
> De : pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] de la part de Paolo Giannozzi [paolo.giannozzi at uniud.it]
> Envoyé : jeudi 6 novembre 2014 17:45
> À : PWSCF Forum
> Objet : Re: [Pw_forum] Non Convergence
>
> Metallic slabs are sometimes difficult to converge.
> I tried with mixing_mod='local-TF' (works better for slabs),
> a smaller mixing_beta (0.1), a larger degauss (0.05) and a
> denser k-point grid (8 8 1) that should yield smoother results,
> and it converges, at least for the reduced cutoff (30/300)
> I tried.
>
> Paolo
>
>
> Try
> On Wed, 2014-11-05 at 15:41 +0000, Elliot Menkah wrote:
> > Hello Everyone,
> > I'm running a geometry optimization calculation(relax) of an 11-layer
> > Nickel slab and I used the deafult nstep (nstep=50) and electron_maxstep
> > (100).
> >
> > My system did not converge with the parameters and configurations set as
> > it run through 100 iterations.
> >
> > Could there be something wrong with the configuration or would I have to
> > increase the  electron_maxstep value?.
> >
> > Please find attached both input and out files in that regard.
> >
> > Thank you
> >
> >
> > Kind Regards,
> >
> > Elliot
> >
> >
> >
> >
> > _______________________________________________
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> > Pw_forum at pwscf.org
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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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--
 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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