# [Pw_forum] electron-phonon calculation stucks

Thu Jul 27 12:09:16 CEST 2017

```Thank you Isaiah for your response.
I am very new to el-ph calculations. By solving examples it seems that by
splitting calculation along irreps calculates phonon dynamical matrices
only not electron-phonon interactions for that specific modes until it runs
ph.x with *recover=.true.* flag, after calculation of all irrep for each
q-points. Is there any way to calculate el-ph interaction as well along
with dynamical matrices for single irrep?

Apparently after calculation of dynamical matrices it should not take very
long to calculate el-ph interaction but in my case it is not going even
after 5*time_for_dynamical_matrices for one q-point. So it seems that
problem lie after calculation of dynamical matrices and when it calculates
el-ph interactions. like my output stays at

*     freq (174 -174) =       2208.9  [cm-1]   --> B_g             R
freq (175 -175) =       2210.2  [cm-1]   --> A_g             R       freq
(176 -176) =       2221.8  [cm-1]   --> B_g             R       freq (177
-177) =       2226.9  [cm-1]   --> A_g             R       freq (178 -178)
=       2246.6  [cm-1]   --> B_u             I       freq (179 -179)
=       2253.9  [cm-1]   --> A_u             I       freq (180 -180)
=       2259.6  [cm-1]   --> A_g             R       freq (181 -181)
=       2264.8  [cm-1]   --> A_u             I       freq (182 -182)
=       2271.1  [cm-1]   --> B_u             I       freq (183 -183)
=       2299.6  [cm-1]   --> B_g             R       freq (184 -184)
=       2317.7  [cm-1]   --> A_u             I       freq (185 -185)
=       2339.6  [cm-1]   --> A_g             R       freq (186 -186)
=       2346.2  [cm-1]   --> B_g             R       freq (187 -187)
=       2359.5  [cm-1]   --> B_u             I       freq (188 -188)
=       2378.8  [cm-1]   --> A_u             I       freq (189 -189)
=       2380.6  [cm-1]   --> A_g             R       freq (190 -190)
=       2496.3  [cm-1]   --> B_u             I       freq (191 -191)
=       2505.6  [cm-1]   --> A_g             R       freq (192 -192)
=       2696.7  [cm-1]   --> A_g             R       electron-phonon
interaction  ...*

Best Regards

On 27 July 2017 at 18:51, Isaiah Moses <imoses87 at gmail.com> wrote:

> Electron-phonon calculation is very very expensive.
> By my little experience, the problem may never be memory and your
> calculation might not have necessarily 'stuck'.
> Your system seems to be very huge and it would take  a lot of time to run.
> Mine is just 11 atoms and the second q-point was not completed after 48
> hours of calculations on 96 processors.
>
> So, the only way of handling such situation is to split your job either
> along q-points, irreps or both.
>
> There are examples on splitting in qe examples in case you are not
> familiar with that.
>
> Kind regards,
> Isaiah
>
> On Thu, Jul 27, 2017 at 8:25 AM, Nadeem Natt <nadeemnatt1 at gmail.com>
> wrote:
>
>> Hi
>> I am doing electron-phonon calculation for picene monoclinic crystal (72
>> atoms). My calculation does not move forward after calculation of dynamical
>> matrices for first q_point (0.0 0.0 0.0). It gets stuck at calculation of
>> electron-phonon interaction. Is this because of memory requirements? Can I
>> know how to calculate memory requirements for this? Thanks
>>
>> Sungkyunkwan University
>>
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>>
>
>
>
> --
> Isaiah Abu Moses
> Physics Department,
> Nigeria
>
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