Symmetries in kgrid.x

Submitted by elchatz on Thu, 07/06/2017 - 09:50

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User questions

Dear all,

I am getting the "kgrid too large compared to unfolded nk" error in the WFN file.

Is there any specific considerations to take care of when using nosym = .true. in the Quantum Epsresso input file?

This obviously produces the following output in the log file:

"No symmetry found"

But the kgrid.log file mentions this:

"symmetries of the Bravais lattice
24"

The other thing that I am thinking is the units of the lattice vectors and the atomic positions which I have declared both in units of alat.

Thank you.

Submitted by elchatz on Thu, 07/06/2017 - 10:13

Note that I have managed to run without problem the same material in bulk without the

nosym = .true.

in QE, however, this is its monolayer form for which the pseudopotential I am using is the only NORMCONS one that gives decent lattice constant results but requires this flag to run properly in the vc-relax, scf and bands calculations.

Submitted by babarker on Thu, 07/06/2017 - 17:24

Hello,

There is probably symmetry information in the WFN file. Use the wfn_rho_vxc_info.x executable to confirm the symmetries in the WFN file are what you expect. Also, in your Espresso input file, set verbosity = 'high' to write out all of the symmetries.

Submitted by elchatz on Tue, 07/11/2017 - 10:31

The symmetries look fine. Can you see any other strange things in this output from your experience?

GW

==================================================================================

FFT grid: 25 25 270

====== SYMMETRIES =====
Number of symmetries: 1
Symmetry type: cubic
Index Rotation matrix Fractional translations
1 : 1 0 0 0 1 0 0 0 1 0.000000 0.000000 0.000000
====== K-POINTS =====
Number of k-points: 35
Number of bands: 52
k-grid: 13 13 1
k-shifts: 0.000000 0.000000 0.500000
[ifmin = lowest occupied band, ifmax = highest occupied band, for each spin]
Index Coordinates (crystal) Weight Number of G-vectors ifmin ifmax
1 0.000000 0.000000 0.500000 0.005917 8676 1 9
2 0.000000 0.076923 0.500000 0.017751 8676 1 9
3 0.000000 0.153846 0.500000 0.017751 8740 1 9
4 0.000000 0.230769 0.500000 0.017751 8748 1 9
5 0.000000 0.307692 0.500000 0.017751 8750 1 9
6 0.000000 0.384615 0.500000 0.017751 8766 1 9
7 0.000000 0.461538 0.500000 0.017751 8782 1 9
8 0.000000 0.538462 0.500000 0.017751 8782 1 9
9 0.000000 0.615385 0.500000 0.017751 8766 1 9
10 0.000000 0.692308 0.500000 0.017751 8750 1 9
11 0.000000 0.769231 0.500000 0.017751 8748 1 9
12 0.000000 0.846154 0.500000 0.017751 8740 1 9
13 0.000000 0.923077 0.500000 0.017751 8676 1 9
14 0.076923 0.076923 0.500000 0.035503 8714 1 9
15 0.076923 0.153846 0.500000 0.035503 8752 1 9
16 0.076923 0.230769 0.500000 0.035503 8768 1 9
17 0.076923 0.307692 0.500000 0.035503 8762 1 9
18 0.076923 0.384615 0.500000 0.035503 8800 1 9
19 0.076923 0.461538 0.500000 0.035503 8816 1 9
20 0.076923 0.538462 0.500000 0.035503 8800 1 9
21 0.076923 0.615385 0.500000 0.035503 8762 1 9
22 0.076923 0.692308 0.500000 0.035503 8768 1 9
23 0.076923 0.769231 0.500000 0.035503 8752 1 9
24 0.153846 0.153846 0.500000 0.035503 8738 1 9
25 0.153846 0.230769 0.500000 0.035503 8768 1 9
26 0.153846 0.307692 0.500000 0.035503 8816 1 9
27 0.153846 0.384615 0.500000 0.035503 8842 1 9
28 0.153846 0.461538 0.500000 0.035503 8842 1 9
29 0.153846 0.538462 0.500000 0.035503 8816 1 9
30 0.153846 0.615385 0.500000 0.035503 8768 1 9
31 0.230769 0.230769 0.500000 0.035503 8814 1 9
32 0.230769 0.307692 0.500000 0.035503 8850 1 9
33 0.230769 0.384615 0.500000 0.035503 8884 1 9
34 0.230769 0.461538 0.500000 0.035503 8850 1 9
35 0.307692 0.307692 0.500000 0.035503 8882 1 9

====================================================================================

QE

=====================================================================================

cryst. s( 1) = ( 1 0 0 )
( 0 1 0 )
( 0 0 1 )

cart. s( 1) = ( 1.0000000 0.0000000 0.0000000 )
( 0.0000000 1.0000000 0.0000000 )
( 0.0000000 0.0000000 1.0000000 )

number of k points= 35
cart. coord. in units 2pi/alat
k( 1) = ( 0.0000000 0.0000000 0.0457340), wk = 0.0118343
k( 2) = ( 0.0000000 0.0892152 0.0457340), wk = 0.0355030
k( 3) = ( 0.0000000 0.1784305 0.0457340), wk = 0.0355030
k( 4) = ( 0.0000000 0.2676457 0.0457340), wk = 0.0355030
k( 5) = ( 0.0000000 0.3568610 0.0457340), wk = 0.0355030
k( 6) = ( 0.0000000 0.4460762 0.0457340), wk = 0.0355030
k( 7) = ( 0.0000000 0.5352915 0.0457340), wk = 0.0355030
k( 8) = ( 0.0000000 0.6245067 0.0457340), wk = 0.0355030
k( 9) = ( 0.0000000 0.7137219 0.0457340), wk = 0.0355030
k( 10) = ( 0.0000000 0.8029372 0.0457340), wk = 0.0355030
k( 11) = ( 0.0000000 0.8921524 0.0457340), wk = 0.0355030
k( 12) = ( 0.0000000 0.9813677 0.0457340), wk = 0.0355030
k( 13) = ( 0.0000000 1.0705829 0.0457340), wk = 0.0355030
k( 14) = ( 0.0772627 0.1338229 0.0457340), wk = 0.0710059
k( 15) = ( 0.0772627 0.2230381 0.0457340), wk = 0.0710059
k( 16) = ( 0.0772627 0.3122533 0.0457340), wk = 0.0710059
k( 17) = ( 0.0772627 0.4014686 0.0457340), wk = 0.0710059
k( 18) = ( 0.0772627 0.4906838 0.0457340), wk = 0.0710059
k( 19) = ( 0.0772627 0.5798991 0.0457340), wk = 0.0710059
k( 20) = ( 0.0772627 0.6691143 0.0457340), wk = 0.0710059
k( 21) = ( 0.0772627 0.7583296 0.0457340), wk = 0.0710059
k( 22) = ( 0.0772627 0.8475448 0.0457340), wk = 0.0710059
k( 23) = ( 0.0772627 0.9367600 0.0457340), wk = 0.0710059
k( 24) = ( 0.1545254 0.2676457 0.0457340), wk = 0.0710059
k( 25) = ( 0.1545254 0.3568610 0.0457340), wk = 0.0710059
k( 26) = ( 0.1545254 0.4460762 0.0457340), wk = 0.0710059
k( 27) = ( 0.1545254 0.5352915 0.0457340), wk = 0.0710059
k( 28) = ( 0.1545254 0.6245067 0.0457340), wk = 0.0710059
k( 29) = ( 0.1545254 0.7137219 0.0457340), wk = 0.0710059
k( 30) = ( 0.1545254 0.8029372 0.0457340), wk = 0.0710059
k( 31) = ( 0.2317882 0.4014686 0.0457340), wk = 0.0710059
k( 32) = ( 0.2317882 0.4906838 0.0457340), wk = 0.0710059
k( 33) = ( 0.2317882 0.5798991 0.0457340), wk = 0.0710059
k( 34) = ( 0.2317882 0.6691143 0.0457340), wk = 0.0710059
k( 35) = ( 0.3090509 0.5352915 0.0457340), wk = 0.0710059

cryst. coord.
k( 1) = ( 0.0000000 0.0000000 0.5000000), wk = 0.0118343
k( 2) = ( 0.0000000 0.0769231 0.5000000), wk = 0.0355030
k( 3) = ( 0.0000000 0.1538462 0.5000000), wk = 0.0355030
k( 4) = ( 0.0000000 0.2307692 0.5000000), wk = 0.0355030
k( 5) = ( 0.0000000 0.3076923 0.5000000), wk = 0.0355030
k( 6) = ( 0.0000000 0.3846154 0.5000000), wk = 0.0355030
k( 7) = ( 0.0000000 0.4615385 0.5000000), wk = 0.0355030
k( 8) = ( 0.0000000 0.5384615 0.5000000), wk = 0.0355030
k( 9) = ( 0.0000000 0.6153846 0.5000000), wk = 0.0355030
k( 10) = ( 0.0000000 0.6923077 0.5000000), wk = 0.0355030
k( 11) = ( 0.0000000 0.7692308 0.5000000), wk = 0.0355030
k( 12) = ( 0.0000000 0.8461538 0.5000000), wk = 0.0355030
k( 13) = ( 0.0000000 0.9230769 0.5000000), wk = 0.0355030
k( 14) = ( 0.0769231 0.0769231 0.5000000), wk = 0.0710059
k( 15) = ( 0.0769231 0.1538462 0.5000000), wk = 0.0710059
k( 16) = ( 0.0769231 0.2307692 0.5000000), wk = 0.0710059
k( 17) = ( 0.0769231 0.3076923 0.5000000), wk = 0.0710059
k( 18) = ( 0.0769231 0.3846154 0.5000000), wk = 0.0710059
k( 19) = ( 0.0769231 0.4615385 0.5000000), wk = 0.0710059
k( 20) = ( 0.0769231 0.5384615 0.5000000), wk = 0.0710059
k( 21) = ( 0.0769231 0.6153846 0.5000000), wk = 0.0710059
k( 22) = ( 0.0769231 0.6923077 0.5000000), wk = 0.0710059
k( 23) = ( 0.0769231 0.7692308 0.5000000), wk = 0.0710059
k( 24) = ( 0.1538462 0.1538462 0.5000000), wk = 0.0710059
k( 25) = ( 0.1538462 0.2307692 0.5000000), wk = 0.0710059
k( 26) = ( 0.1538462 0.3076923 0.5000000), wk = 0.0710059
k( 27) = ( 0.1538462 0.3846154 0.5000000), wk = 0.0710059
k( 28) = ( 0.1538462 0.4615385 0.5000000), wk = 0.0710059
k( 29) = ( 0.1538462 0.5384615 0.5000000), wk = 0.0710059
k( 30) = ( 0.1538462 0.6153846 0.5000000), wk = 0.0710059
k( 31) = ( 0.2307692 0.2307692 0.5000000), wk = 0.0710059
k( 32) = ( 0.2307692 0.3076923 0.5000000), wk = 0.0710059
k( 33) = ( 0.2307692 0.3846154 0.5000000), wk = 0.0710059
k( 34) = ( 0.2307692 0.4615385 0.5000000), wk = 0.0710059
k( 35) = ( 0.3076923 0.3076923 0.5000000), wk = 0.0710059

Dense grid: 70069 G-vectors FFT dimensions: ( 25, 25, 270)

Submitted by babarker on Tue, 07/11/2017 - 21:18

Hello,

I believe you should recalculate without the half-shift in the third reciprocal lattice vector. It looks like you're doing a (quasi?) two-dimensional calculation, in which case your sampling needs to be in the plane (k1, k2, 0.0).

Let me know if that helps.

Best,
Brad

Submitted by elchatz on Thu, 07/13/2017 - 03:56

I did this after trying without the shift, because I was trying to keep as many parameters similar to the bulk system that worked.

It is not working without the shift either. It gives me the same error.

The other question that I just had is: Do I get rid of the vaccum for 2D systems in the GW calculation? Could the problem be related to this?

Submitted by elchatz on Fri, 07/14/2017 - 02:11

The error seems to have dissapeared after converting lattice vectors and atomic positions in angstrom and cutting at four decimal places. I am unsure if there were any mistakes that I hadan't noticed.

The point is that I am now creating 169 KPOINTS for the 13x13x1 grid instead of the 35 I was producing earlier.

During relaxation, with the automatic keyword, QE was producing 85 KPOINTS for 13x13x1