[Pw_forum] Phonon calculation

[Uri Argaman]

Thank you for your reply.

>* It's worth to set nimage equal to the number of q-points *>* in the phonon calculation? *
not necessarily so. Different wave-vectors may have different
workloads: not by order of magnitudes, but a low-symmetry
wave-vector may easily take 5 times more CPU than a high-symmetry
one.

But still as far as I understand is there any cost of doing it?
Am I loosing somthing by puting nimage=number of q-points in the dyn0 file?
I understand that some of the parallel images will be finished before the other,
But there is nothing I can do to speed it even more.

>* In addition I want to ask how the complexity of the phonon calculation*>* depends on the number of the k-points (in the PW calculation) *
roughly linearly, but the number of actual k-points in phonon
calculations depends upon the symmetry and the wave-vector

>* and how the number of k-points affects the accuracy of the phonon*>* calculation. *
more or less (more rather than less) in the same way as it affects
the calculation of other structural properties; quantities related
to the electric field (effective charges and dielectric tensors)
tend to converge more slowly with the number of k-points

P.

-- 
Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222



On 7 October 2013 09:48, Uri Argaman <argamanu at post.bgu.ac.il> wrote:

> It's worth to set nimage equal to the number of q-points in the phonon
> calculation? In addition I want to ask how the complexity of the phonon
> calculation depends on the number of the k-points (in the PW calculation)
> and how the number of k-points affects the accuracy of the phonon
> calculation.
>
> thank you
>
> Uri Argaman
>
> Ben-Gurion University, Israel
>
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