EPW Forum

Posted: **Wed Oct 06, 2021 7:59 pm**

Dear experts and users,

I have encountered a problem with anomalously large electron-phonon coupling in my calculations.
I have read several posts concerning this problem, and done several checks to see if something was wrong.
1. Wannierization is alright. The spreads are small, and the W90 bands are identical to the DFT ones.

Code: Select all

Final State
  WF centre and spread    1  ( -0.000000, -0.006355,  3.124586 )     1.61613462
  WF centre and spread    2  ( -0.000000,  0.015011,  3.122453 )     1.79888605
  WF centre and spread    3  ( -0.000000, -0.015070,  3.122418 )     1.79847202
  WF centre and spread    4  (  0.000000,  0.158487,  3.116459 )     1.79946429
  WF centre and spread    5  ( -0.000000, -0.150425,  3.116332 )     1.80460140
  WF centre and spread    6  (  0.000000,  0.006355,  9.417980 )     1.61613352
  WF centre and spread    7  ( -0.000000, -0.015013,  9.420114 )     1.79889375
  WF centre and spread    8  (  0.000000,  0.015072,  9.420148 )     1.79847975
  WF centre and spread    9  ( -0.000000, -0.158487,  9.426108 )     1.79946161
  WF centre and spread   10  (  0.000000,  0.150425,  9.426235 )     1.80459878
  WF centre and spread   11  (  1.727612,  0.995223,  1.376172 )     1.99038830
  WF centre and spread   12  (  1.727612,  0.977771,  1.481458 )     1.92301330
  WF centre and spread   13  (  1.727612,  1.018705,  1.481455 )     1.92321317
  WF centre and spread   14  ( -0.000000,  1.996840,  7.715918 )     2.01666448
  WF centre and spread   15  (  0.000000,  2.012433,  7.802887 )     1.92967817
  WF centre and spread   16  ( -0.000000,  1.975993,  7.802897 )     1.92988829
  WF centre and spread   17  ( -0.000000,  1.997089, 11.166395 )     1.99039532
  WF centre and spread   18  (  0.000000,  2.014541, 11.061109 )     1.92302111
  WF centre and spread   19  ( -0.000000,  1.973608, 11.061113 )     1.92322102
  WF centre and spread   20  (  1.727612,  0.995473,  4.826646 )     2.01666330
  WF centre and spread   21  (  1.727612,  0.979878,  4.739677 )     1.92967463
  WF centre and spread   22  (  1.727612,  1.016320,  4.739666 )     1.92988469
  Sum of centres and spreads ( 10.365674, 17.953873,137.968226 )    41.06083156
 
         Spreads (Ang^2)       Omega I      =    39.123517350
        ================       Omega D      =     0.047965860
                               Omega OD     =     1.889352180
    Final Spread (Ang^2)       Omega Total  =    41.060835391
 ------------------------------------------------------------------------------

2. All the necessary quantities decay well (see the picture)

: decay.png (48.8 KiB) Viewed 3496 times

3. Using the bandplot = .true. variable I checked electronic and phonon bands again, and they are fine.
4. I don't use assume_isolated in PW which, as I understood, can lead to troubles.

Could you please tell me what else to check?

Thanks you very much.

Posted: **Wed Oct 06, 2021 9:47 pm**

Hi Chill,

I can only guess, this may be because your 'dvscf*' files are not correctly written. Could you check their sizes? Are all the same? Did you have to restart your phonon or you did in a single run? I am asking this because I had the same issue long back when I restarted my phonon for a q-point. My problem was solved after I re-ran phonon for that q-point from scratch, and replaced the dvscf and dyn. This is just a guess, not sure.

Please, also provide your epw output file, if something can be figured out.

Happy EPWing,
Hari Paudyal

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