weird symmetry problem with electric fields (lelfield

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weird symmetry problem with electric fields (lelfield

Postby chwolf » Fri Feb 02, 2018 2:35 pm

Dear all,

I am currently trying to calculate the effect of an electric field (PWSCF: lelfield-.t., efield_cart(3)=0.002). When run without field the absorption spectrum (-o c) looks quite nice, but when the lelfield is turned on, it seems that QE messes up the kpoints and I am left with an error complaining about

Code: Select all
[03] Transferred momenta grid
 =============================


 IBZ Q-points :  7
 BZ  Q-points : 12

 Q [00001] : 0.00      0.00      0.00     (iku) * weight   0.08333
 Q [00002] :  0.08333   0.16667   0.00000 (iku) * weight  0.166667
 Q [00003] : 0.166667  0.333333  0.000000 (iku) * weight  0.166667
 Q [00004] :-0.250000 -0.500000  0.000000 (iku) * weight   0.08333
 Q [00005] : 0.250000  0.166667  0.000000 (iku) * weight  0.166667
 Q [00006] : 0.333333  0.333333  0.000000 (iku) * weight  0.166667
 Q [00007] : 0.500000  0.333333  0.000000 (iku) * weight  0.166667
 
 Q [00001] : 0.00      0.00      0.00     (cc ) * weight   0.08333
 Q [00002] :  0.04318   0.07478   0.00000 (cc ) * weight  0.166667
 Q [00003] : 0.086354  0.149569  0.000000 (cc ) * weight  0.166667
 Q [00004] :-0.129531 -0.224353  0.000000 (cc ) * weight   0.08333
 Q [00005] : 0.129531  0.074785  0.000000 (cc ) * weight  0.166667
 Q [00006] : 0.172707  0.149569  0.000000 (cc ) * weight  0.166667
 Q [00007] : 0.259061  0.149569  0.000000 (cc ) * weight  0.166667

 :: Indices: polarization function

 [ERROR] STOP signal received while in :[03] Transferred momenta grid

 [ERROR] Error search for G=G1-G2 !!


interestingly the nscf k points (manual input) are the same and so are the scf/nscf kpoints from the output. However, above section from thh run without field reads

Code: Select all
 IBZ Q-points :  7
 BZ  Q-points :  36

 Q [00001] : 0.00      0.00      0.00     (iku) * weight   0.02778
 Q [00002] :  0.08333   0.16667   0.00000 (iku) * weight  0.166667
 Q [00003] : 0.166667  0.333333  0.000000 (iku) * weight  0.166667
 Q [00004] :-0.250000 -0.500000  0.000000 (iku) * weight   0.08333
 Q [00005] : 0.250000  0.166667  0.000000 (iku) * weight  0.166667
 Q [00006] : 0.333333  0.333333  0.000000 (iku) * weight  0.333333
 Q [00007] : 0.500000  0.333333  0.000000 (iku) * weight   0.05556
 
 Q [00001] : 0.00      0.00      0.00     (cc ) * weight   0.02778
 Q [00002] :  0.04318   0.07478   0.00000 (cc ) * weight  0.166667
 Q [00003] : 0.086354  0.149569  0.000000 (cc ) * weight  0.166667
 Q [00004] :-0.129531 -0.224353  0.000000 (cc ) * weight   0.08333
 Q [00005] : 0.129531  0.074784  0.000000 (cc ) * weight  0.166667
 Q [00006] : 0.172707  0.149569  0.000000 (cc ) * weight  0.333333
 Q [00007] : 0.259061  0.149569  0.000000 (cc ) * weight   0.05556

 :: Indices: polarization function
 :: Indices: Self-Energy

i.e. the BZ points are different.

does anyone know a remedy to this behavior?

scf/nscf/yambo report files are attached, the PP is from the ONCV repository and the system is a double layer of graphene.

Any help is greatly appreciated!

Best,
Chris
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Christoph Wolf

Postech university, South Korea
chwolf@postech.ac.kr
chwolf
 
Posts: 30
Joined: Mon Jul 11, 2016 2:11 pm
Location: South Korea

Re: weird symmetry problem with electric fields (lelfield

Postby Daniele Varsano » Mon Feb 05, 2018 5:08 pm

Dear Chris,

at first look, it seems k points in the IBZ are the same, with different weights due to the reduced symmetry properties of the system.
We will try to reproduce your error and spot the problem,

Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/
User avatar
Daniele Varsano
 
Posts: 2027
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Re: weird symmetry problem with electric fields (lelfield

Postby Daniele Varsano » Fri Feb 09, 2018 4:05 pm

Dear Chris,
I've been checking a bit your problem and there is a problem coming from the mesh of QE and the time-reversal symmetry added by Yambo.
In order to solve it you can add in your nscf input file the flag:
Code: Select all
nosym=.true.

together with an automatic generation of k points.
Code: Select all
e.g.
K_POINTS (automatic)
3 3 1    0 0 0


If you have a reason to use a user-defined grid, you can still do that, but when adding the nosym=.true. option, you need to define a regular grid in the whole BZ, i.e. a 9 point grid in your case, which should not be difficult to derive.

Best,

Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/
User avatar
Daniele Varsano
 
Posts: 2027
Joined: Tue Mar 17, 2009 2:23 pm


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