maximum allowed k and q grids in EPW

[mmkhatami]

Dear developers,

I want to extract Phonon dispersion of 2D materials and to obtain a good plot I think I should increase k and q grids to as high as possible. When I increase the kgrid(in nscf file and then in EPW) up to 26*26*1 and the q grid(in ph file and then in EPW) up to 13*13*1, it can be run but further increase in these values turns into this error:
-------------------------------------------------------------------
Wannierization on 28 x 28 x 1 electronic grid
-------------------------------------------------------------------

Spin CASE ( default = unpolarized )

Initializing Wannier90


Initial Wannier projections

( 0.00000 0.00000 0.00000) : l = -3 mr = 1
( 0.00000 0.00000 0.00000) : l = -3 mr = 2
( 0.00000 0.00000 0.00000) : l = -3 mr = 3
( 0.00000 0.00000 0.00000) : l = -3 mr = 4
( 0.33333 0.66667 0.02200) : l = -3 mr = 1
( 0.33333 0.66667 0.02200) : l = -3 mr = 2
( 0.33333 0.66667 0.02200) : l = -3 mr = 3
( 0.33333 0.66667 0.02200) : l = -3 mr = 4

- Number of bands is ( 8)
- Number of total bands is ( 8)
- Number of excluded bands is ( 0)
- Number of wannier functions is ( 8)
- All guiding functions are given

Reading data about k-point neighbours

- All neighbours are found

AMN
k points = 784 in 34 pools
1 of 24 on ionode
2 of 24 on ionode
3 of 24 on ionode
4 of 24 on ionode
5 of 24 on ionode
6 of 24 on ionode
7 of 24 on ionode
8 of 24 on ionode
9 of 24 on ionode
10 of 24 on ionode
11 of 24 on ionode
12 of 24 on ionode
13 of 24 on ionode
14 of 24 on ionode
15 of 24 on ionode
16 of 24 on ionode
17 of 24 on ionode
18 of 24 on ionode
19 of 24 on ionode
20 of 24 on ionode
21 of 24 on ionode
22 of 24 on ionode
23 of 24 on ionode
24 of 24 on ionode

AMN calculated

MMN
k points = 784 in 34 pools
1 of 24 on ionode
2 of 24 on ionode
3 of 24 on ionode
4 of 24 on ionode
5 of 24 on ionode
6 of 24 on ionode
7 of 24 on ionode
8 of 24 on ionode
9 of 24 on ionode
10 of 24 on ionode
11 of 24 on ionode
12 of 24 on ionode
13 of 24 on ionode
14 of 24 on ionode
15 of 24 on ionode
16 of 24 on ionode
17 of 24 on ionode
18 of 24 on ionode
19 of 24 on ionode
20 of 24 on ionode
21 of 24 on ionode
22 of 24 on ionode
23 of 24 on ionode
24 of 24 on ionode
MMN calculated

Running Wannier90
wann_main: problem computing schur form 1
Error: examine the output/error file for details
--------------------------------------------------------------------------
mpirun has exited due to process rank 0 with PID 0 on
node khatami-HPC exiting improperly. There are three reasons this could occur:

1. this process did not call "init" before exiting, but others in
the job did. This can cause a job to hang indefinitely while it waits
for all processes to call "init". By rule, if one process calls "init",
then ALL processes must call "init" prior to termination.

2. this process called "init", but exited without calling "finalize".
By rule, all processes that call "init" MUST call "finalize" prior to
exiting or it will be considered an "abnormal termination"

3. this process called "MPI_Abort" or "orte_abort" and the mca parameter
orte_create_session_dirs is set to false. In this case, the run-time cannot
detect that the abort call was an abnormal termination. Hence, the only
error message you will receive is this one.

This may have caused other processes in the application to be
terminated by signals sent by mpirun (as reported here).

You can avoid this message by specifying -quiet on the mpirun command line.
--------------------------------------------------------------------------

I have tried k grids/q grids of 28*28*1/14*14*1, 30*30*1/15*15*1, and 32*32*1/16*16*1 but all turn into the same error. Therefore, I want to ask if there is any maximum value for k and q grids in EPW.

Regards,
Mohammad Mahdi Khatami

[sponce]

Dear Mohammad Mahdi Khatami,

That is a problem with the wannier90 software that EPW calls.

The issue is located in wannier90-2.1.0/src/wannierise.F90 at line 866

It seems the code return an error while computing the eigenvalues of an N-by-N complex nonsymmetric matrix. You can look at the lapack call http://www.netlib.org/lapack/explore-ht ... 06c86ce53b

I am not sure why this happens for you if all you did is increasing the grid keeping everything the same and it is working for smaller grids.

You might want to ask the wannier90 team directly on their forum/mailing list

Best wishes,
Samuel