[Pw_forum] Problem with high accuracy and parallel ph.x (Mohammad Saghayezhian)

[Mohammad Saghayezhian]

Dear Andrea,

Thanks for reply.

The nkp in my calculation is far less than 40000. As I know, the symmetry
reduces nkp,
therefore for a mesh of 30*30*28 the max nkp is 25200, So if the problem
rooted in max nkp parameter,
above mesh should not make any problem, there are some
tests that I did for checking the valid nkp and cut-off energy:
Cut-off(Ry) , Kpoints: 33, 22*22*18 (OK)
                                35, 25*25*22 (OK)
                                35, 30*30*26 ()
                                38, 22*22*18 (OK)
                                38, 30*30*26 (Failed)
                                40, 30*30*26 (Failed)
All of above number kpoints are lower that nkp max (40000). I also run the
calculation
without npool option to provide higher memory for large cut-off. but still I
wonder why
the last two calculation did not worked!

Could it be due to optimization deficiency in compilation of ph.x files?
Please take a look at this links:
http://www.democritos.it/pipermail/pw_forum/2005-February/002070.html
 http://www.democritos.it/pipermail/pw_forum/2005-February/002074.html
Thanks a lot



On Thu, Fri, 01 Jul 2011 10:01:48 +0200,  Andrea Dal Corso wrote:
>Please note that the maximum number of k points is still a parameter in
>QE (presently set to 40000), so to make phonon calculations with a very
>large mesh of k points you have to increase the value of npk in
>Modules/parameters.f90.


>HTH,

>Andrea



On Thu, 2011-06-30 at 11:58 +0330, Mohammad Saghayezhian wrote:
> Dear All,
>
> When I perform the scf calculation with high kp (45 45 45) and cut-off
> (42 Ry), the parallel execution ph.x fails and stops (q-points in
> ph.in: 4 4 3). but lowering the kp (15 15 15) and cut-off (22 Ry)
> solves the problem and the parallel ph.x goes on without any problem.
> Does this mean that I can not calculate phonon spectra with this
> accuracy?
> Also, the calculations are for metals.
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Mohammad Saghayezhian
Computational Condensed Matter Research Lab
Physics Department, Isfahan University of Technology, Isfahan, Iran

Tel lab: +98 311 391 3731     Fax Office: +98311 391 3746
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