[Pw_forum] epsilon.x

[Andrea Ferretti]

Dear Pashangpour,

what I meant is that the meaning of the variables intersmear and 
intrasmear of epsilon is quite similar to that of degauss in DOS or 
projwfc, and that convergences should be studied in a similar way...
(note that very often kpt meshes denser than those used for scf runs are 
needed to converge DOS/projwfc/epsilon calculations)

Andrea

> I mean inter and intera smearings in inputpp of epsilon calculation not in inputscf. Do you mean I can set them similar
> kpt, Ecuts and smearing in scf input?
> Thanks
> M Pashangpour
> IIAU,Tehran,Iran
> 
> Sent from my iPhone
> 
> On 23 Nov 2016, at 19:56, Andrea Ferretti <andrea.ferretti at unimore.it> wrote:
> 
> 
>
>       Dear Pashangpour,
>
>       the idea is very similar to the usual kpt convergence
>       vs smearing parameter for a DOS calculation.
>
>       At variance with scf runs, here you are computing a spectral quantity
>       (the dielectric function as a function of the frequency), meaning that you
>       may need a (much) finer mesh of kpts.
>
>       In general, the larger the smearing, the lower the resolution of your
>       spectrum (in the simplest case you are replacing dirac's deltas with
>       gaussians), while the larger the kpt mesh that you use, the smaller the
>       smearing parameter can be...
>
>       I would follow a recipe like this:
>       * set the smearing and converge the spectrum wrt kpts
>       * if the accuracy of the spectrum (ie the resolution of its features) is
>         ok with you, exit(),
>         otherwise reduce the smearing parameter and iterate
>       * by reducing the smearing you should expect to converge with a denser
>         mesh of kpts  (a rule of thumb could be dk * delta ~ constant, where
>         dk is the kpt grid spacing and delta the smearing parameter.. though
>         it probably depends on the system and on your requirements)
>
>       Andrea
> 
>
>             Dear all
>
>             How can I find suitable value of intersmear and intrasmear in epsioln calculation via epsilon.x?
>
>             Thanks in advance
>
>             M. Pashangpour
>
>             PhD of physics
>
>             IAU,Tehran,Iran
> 
>
>             Sent from my iPhone
>
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> 
>
>       --
>       Andrea Ferretti, PhD
>       S3 Center, Istituto Nanoscienze, CNR
>       via Campi 213/A, 41125, Modena, Italy
>       Tel: +39 059 2055322;  Skype: andrea_ferretti
>       URL: http://www.nano.cnr.it
>
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>

-- 
Andrea Ferretti, PhD
S3 Center, Istituto Nanoscienze, CNR
via Campi 213/A, 41125, Modena, Italy
Tel: +39 059 2055322;  Skype: andrea_ferretti
URL: http://www.nano.cnr.it