EPW Forum

Dear all,

in an attempt to calculate the electron phonon coupling of a system I am working on, the code stopped with an error:

===================================================================
irreducible q point # 28
===================================================================


q( 143 ) = ( 0.3333333 0.5773503 -0.0769231 )
q( 144 ) = ( -0.3333333 0.5773503 0.0769231 )

Writing epmatq on .epb files


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
from elphon_shuffle_wrap : error # 144
nqc .ne. nq1*nq2*nq3
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

stopping ...


in an scf calculation the grid was 12 12 12 0 0 0
In the nscf I used a grid of 6x6xx =216 points
the phonons were calculated on an nq1=6 nq2=6 nq3=6 (28 phonon points). i guess the code complains that the number of points is 144 and not equal to 216. But what has happened and how to resolve this?

thanks

Dear eliephys78,

Could you give us the list of q-points (the 28 ones) that is reported in the ph.out file.

Then make sure that the list of q-point that you provide in the epw.in file is exactly the same.

Note that 1.0 0.0 0.0 is different from -1.0 0.0 0.0 even in crystal coordinate. This is because of a phase.

You should therefore have the exact same list (with the same number of digits).

The code should indeed be able to reconstruct from the 28 q-points the full 216 q-points.

Here it seems the code could not find all of them.

Best,

Samuel

The list of q points as reported in the ph.out file is:

Dynamical matrices for ( 6, 6, 6,) uniform grid of q-points
( 28q-points):
N xq(1) xq(2) xq(3)
1 0.00000 0.00000 0.00000
2 0.00000 0.00000 0.02564
3 0.00000 0.00000 0.05128
4 0.00000 0.00000 -0.07692
5 0.00000 0.19245 0.00000
6 0.00000 0.19245 0.02564
7 0.00000 0.19245 0.05128
8 0.00000 0.19245 -0.07692
9 0.00000 0.38490 0.00000
10 0.00000 0.38490 0.02564
11 0.00000 0.38490 0.05128
12 0.00000 0.38490 -0.07692
13 0.00000 -0.57735 0.00000
14 0.00000 -0.57735 0.02564
15 0.00000 -0.57735 0.05128
16 0.00000 -0.57735 -0.07692
17 0.16667 0.28868 0.00000
18 0.16667 0.28868 0.02564
19 0.16667 0.28868 0.05128
20 0.16667 0.28868 -0.07692
21 0.16667 0.48113 0.00000
22 0.16667 0.48113 0.02564
23 0.16667 0.48113 0.05128
24 0.16667 0.48113 -0.07692
25 0.33333 0.57735 0.00000
26 0.33333 0.57735 0.02564
27 0.33333 0.57735 0.05128
28 0.33333 0.57735 -0.07692

However in my previous calculations I have inluded the list in the same order as the ph,out but taken from the scf.out file (which has more digits and inludes the corresponding weights!). this is when the code complained with the above error.

What I have done now is that I have included the same list but with less digits (as can be seen from the ph.out and without the weights). the code performed the wannier calculations and just stopped with no errors. Do I have to include the weights of the points as obtained from scf.out?

Regards

Hello,

In you epw.in file you should put




The value of the weight do not matter but they have to be there.

I have changed the number of digits to be the same as the ph.out file (which are less than the scf.out!), this produced an error

q-vectors are not commensurate.

I have added again the extra digits (to become exactly the same as the scf.out) and I got the same error again: stopping at point 144 and crashing:

q( 143 ) = ( 0.3333333 0.5773503 -0.0769231 )
q( 144 ) = ( -0.3333333 0.5773503 0.0769231 )

Writing epmatq on .epb files


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
from elphon_shuffle_wrap : error # 144
nqc .ne. nq1*nq2*nq3
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

stopping ...

So i guess something else is going on. My epw input file is:

&inputepw
prefix = 'mos2',
amass(1) = 32.07
amass(2) = 95.94
outdir = '/home/emoujaes//Elie/MoS2-EPW/epw/OUT/'

elph = .true.
kmaps = .false.
epbwrite = .true.
ephwrite = .true.

parallel_k = .true.
parallel_q = .false.

epf_mem = .true.
etf_mem = .true.

nbndsub = 11
nbndskip = 0

wannierize = .true.
num_iter = 300
proj(1) = 'S:p'
proj(2) = 'Mo:d'
dis_froz_min = -8.0d0
dis_froz_max = 3.0d0


iverbosity = 0
degaussq=0.5

elinterp = .true.
phinterp = .true.

tshuffle2 = .true.
tphases = .false.

elecselfen = .false.
phonselfen = .true.
fly = .true.
a2f = .true.

fsthick = 1
eptemp = 300
degaussw = 0.15


dvscf_dir = '/home/emoujaes/Elie/MoS2-EPW/phonons/save'

nk1 = 6
nk2 = 6
nk3 = 6

nq1 = 6
nq2 = 6
nq3 = 6


nqf1 = 12
nqf2 = 12
nqf3 = 12
nkf1 = 12
nkf2 = 12
nkf3 = 12
/
28 cartesian
0.0000000 0.0000000 0.0000000 1.0
0.0000000 0.0000000 0.0256410 1.0
0.0000000 0.0000000 0.0512820 1.0
0.0000000 0.0000000 -0.0769231 1.0
0.0000000 0.1924501 0.0000000 1.0
0.0000000 0.1924501 0.0256410 1.0
0.0000000 0.1924501 0.0512820 1.0
0.0000000 0.1924501 -0.0769231 1.0
0.0000000 0.3849002 0.0000000 1.0
0.0000000 0.3849002 0.0256410 1.0
0.0000000 0.3849002 0.0512820 1.0
0.0000000 0.3849002 -0.0769231 1.0
0.0000000 -0.5773503 0.0000000 1.0
0.0000000 -0.5773503 0.0256410 1.0
0.0000000 -0.5773503 0.0512820 1.0
0.0000000 -0.5773503 -0.0769231 1.0
0.1666667 0.2886751 0.0000000 1.0
0.1666667 0.2886751 0.0256410 1.0
0.1666667 0.2886751 0.0512820 1.0
0.1666667 0.2886751 -0.0769231 1.0
0.1666667 0.4811252 0.0000000 1.0
0.1666667 0.4811252 0.0256410 1.0
0.1666667 0.4811252 0.0512820 1.0
0.1666667 0.4811252 -0.0769231 1.0
0.3333333 0.5773503 0.0000000 1.0
0.3333333 0.5773503 0.0256410 1.0
0.3333333 0.5773503 0.0512820 1.0
0.3333333 0.5773503 -0.0769231 1.0


and the q-points produced by ph.x are:

Dynamical matrices for ( 6, 6, 6,) uniform grid of q-points
( 28q-points):
N xq(1) xq(2) xq(3)
1 0.00000 0.00000 0.00000
2 0.00000 0.00000 0.02564
3 0.00000 0.00000 0.05128
4 0.00000 0.00000 -0.07692
5 0.00000 0.19245 0.00000
6 0.00000 0.19245 0.02564
7 0.00000 0.19245 0.05128
8 0.00000 0.19245 -0.07692
9 0.00000 0.38490 0.00000
10 0.00000 0.38490 0.02564
11 0.00000 0.38490 0.05128
12 0.00000 0.38490 -0.07692
13 0.00000 -0.57735 0.00000
14 0.00000 -0.57735 0.02564
15 0.00000 -0.57735 0.05128
16 0.00000 -0.57735 -0.07692
17 0.16667 0.28868 0.00000
18 0.16667 0.28868 0.02564
19 0.16667 0.28868 0.05128
20 0.16667 0.28868 -0.07692
21 0.16667 0.48113 0.00000
22 0.16667 0.48113 0.02564
23 0.16667 0.48113 0.05128
24 0.16667 0.48113 -0.07692
25 0.33333 0.57735 0.00000
26 0.33333 0.57735 0.02564
27 0.33333 0.57735 0.05128
28 0.33333 0.57735 -0.07692

Dear eliephys78,

Are you using the latest EPW version?
The EPW available in QE 5.4.0 is the latest one.

I notice that you have for example 'epf_mem = .true.' which is not a valid EPW input variable anymore.

See http://epw.org.uk/Documentation/Inputs for a list of input variables.

Best,

Samuel

Dear Samuel,

Thanks for your reply. I am using EPW-3.0.0. It works perfectly fine for systems that I have tried like Pb and Al. however it fails and gives the error I discussed above for my system. I do not think the version is the culprit. I am trying to figure out why this is happening and the code only produces 144 points and not the whole 216 points. I still have problems with this. Any other particular reasons for the error:

Writing epmatq on .epb files


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
from elphon_shuffle_wrap : error # 144
nqc .ne. nq1*nq2*nq3
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

stopping ...

Dear eliephys78,

I strongly suggest you to use the latest EPW-4 version.

For example, time reversal symmetry was not working in EPW-3.

If you really want to stick to EPW3, you can go around that by explicitly computing the -q points with the ph code.

If this is the issue, the technical explanation is given in section 13 (appendix) of that paper http://arxiv.org/pdf/1604.03525v1.pdf

Best,

Samuel

Thanks for your reply.

I will be downloading QE-5.4.0 together with EPW4 and will verify if the error persists.