q-point reduction
Posted: Mon Sep 19, 2011 2:47 pm
Hi
I am a bit confused about the way yambo handles k-points and q-points. I have run an abinit calculation with a 2x2x2 Monkhorst-Pack k-point mesh,
which reduces to two k-points in the IBZ. When I then use a2y and initialize yambo the two irreducible k-points are read correctly, but the r_setup file says the k-point grid latttice is 4x4x4 with 32 k-points in the full Brillouin Zone? However, the weights of the two IBZ k-points are still given correctly by 0.25 and 0.75.
In the q-point part of r_setup, it also says that there is 32 q-points in the full Brillouin zone (and 6 in the IBZ), and the Gamma q-point has a weight of 1/32. I would expect that the q-point grid is identical to the k-point grid but shifted rigidly to the Gamma point and if the k-point grid is really 2x2x2 there should not be any irreducible q-points with weights larger than 1/8. Anyway, I do not understand the 32 grid points in both the q and k mesh. I have attached some part of the r_setup file below.
Hope to hear from you
BR
Thomas Olsen
Post Doc
Technical University of Denmark
[02.04] K-grid lattice
======================
Compatible Grid is 3D
B1 [rlu]= 0.250000 0.000000 -0.250000
B2 = 0.000000 0.250000 0.250000
B3 = 0.250000 -0.250000 0.000000
Grid dimensions : 4 4 4
K lattice UC volume [au]: 0.02870
[02.05] Energies [ev] & Occupations
===================================
Fermi Level [ev]: 5.514878
Electronic Temp. [ev K]: 0.000 0.000
Bosonic Temp. [ev K]: 0.000 0.000
States summary : Full Metallic Empty
0001-0004 0005-0050
Indirect Gaps [ev]: 2.189679 2.667022
Direct Gaps [ev]: 2.667022 3.636977
X BZ K-points : 32
Energy unit is electronVolt [eV]
*X* K [1] : 0.250000 0.250000 0.250000 (iku) * Comp.s 1239 * weight 0.250000
E -10.41180 -3.18791 0.00000 0.00000 2.66702 4.23645 4.23645 7.45231
E 7.94651 7.94651 9.49662 12.32970 15.30944 15.30944 18.40633 18.48032
E 18.48032 20.43920 24.59591 24.59591 26.81704 26.81704 28.16491 29.34568
E 30.83834 32.43739 32.43739 33.86847 33.86847 34.88784 34.88784 37.82172
E 38.72376 38.87284 38.87284 40.19839 40.58587 41.63432 41.63432 42.41716
*X* K [2] : 0.750000 -0.250000 -0.250000 (iku) * Comp.s 1239 * weight 0.750000
E -8.487826 -5.636255 -2.799987 -1.447297 2.189679 5.123933 6.387629 6.637626
E 10.80155 11.25749 12.87792 13.21874 13.51601 17.33978 18.39631 19.08792
E 19.96195 20.07125 20.42633 23.34865 24.23030 25.70242 25.91661 28.12370
E 29.54890 29.82261 29.91684 31.20166 32.50274 34.73485 35.34467 36.54069
E 37.04201 37.84974 39.19511 40.69464 42.50407 43.69879 44.95288 44.98957
[03] Transferred momenta grid
=============================
IBZ Q-points : 6
BZ Q-points : 32
Q [00001] : 0.000 0.000 0.000 (iku) * weight 0.03125
Q [00002] :-0.500000 0.000000 -0.500000 (iku) * weight 0.375000
Q [00003] :-0.500000 -0.500000 -0.500000 (iku) * weight 0.125000
Q [00004] : 0.000000 -0.500000 0.000000 (iku) * weight 0.187500
Q [00005] :-1.000000 -0.500000 0.000000 (iku) * weight 0.187500
Q [00006] :-1.000000 0.000000 0.000000 (iku) * weight 0.09375
:: Indices: polarization function
I am a bit confused about the way yambo handles k-points and q-points. I have run an abinit calculation with a 2x2x2 Monkhorst-Pack k-point mesh,
which reduces to two k-points in the IBZ. When I then use a2y and initialize yambo the two irreducible k-points are read correctly, but the r_setup file says the k-point grid latttice is 4x4x4 with 32 k-points in the full Brillouin Zone? However, the weights of the two IBZ k-points are still given correctly by 0.25 and 0.75.
In the q-point part of r_setup, it also says that there is 32 q-points in the full Brillouin zone (and 6 in the IBZ), and the Gamma q-point has a weight of 1/32. I would expect that the q-point grid is identical to the k-point grid but shifted rigidly to the Gamma point and if the k-point grid is really 2x2x2 there should not be any irreducible q-points with weights larger than 1/8. Anyway, I do not understand the 32 grid points in both the q and k mesh. I have attached some part of the r_setup file below.
Hope to hear from you
BR
Thomas Olsen
Post Doc
Technical University of Denmark
[02.04] K-grid lattice
======================
Compatible Grid is 3D
B1 [rlu]= 0.250000 0.000000 -0.250000
B2 = 0.000000 0.250000 0.250000
B3 = 0.250000 -0.250000 0.000000
Grid dimensions : 4 4 4
K lattice UC volume [au]: 0.02870
[02.05] Energies [ev] & Occupations
===================================
Fermi Level [ev]: 5.514878
Electronic Temp. [ev K]: 0.000 0.000
Bosonic Temp. [ev K]: 0.000 0.000
States summary : Full Metallic Empty
0001-0004 0005-0050
Indirect Gaps [ev]: 2.189679 2.667022
Direct Gaps [ev]: 2.667022 3.636977
X BZ K-points : 32
Energy unit is electronVolt [eV]
*X* K [1] : 0.250000 0.250000 0.250000 (iku) * Comp.s 1239 * weight 0.250000
E -10.41180 -3.18791 0.00000 0.00000 2.66702 4.23645 4.23645 7.45231
E 7.94651 7.94651 9.49662 12.32970 15.30944 15.30944 18.40633 18.48032
E 18.48032 20.43920 24.59591 24.59591 26.81704 26.81704 28.16491 29.34568
E 30.83834 32.43739 32.43739 33.86847 33.86847 34.88784 34.88784 37.82172
E 38.72376 38.87284 38.87284 40.19839 40.58587 41.63432 41.63432 42.41716
*X* K [2] : 0.750000 -0.250000 -0.250000 (iku) * Comp.s 1239 * weight 0.750000
E -8.487826 -5.636255 -2.799987 -1.447297 2.189679 5.123933 6.387629 6.637626
E 10.80155 11.25749 12.87792 13.21874 13.51601 17.33978 18.39631 19.08792
E 19.96195 20.07125 20.42633 23.34865 24.23030 25.70242 25.91661 28.12370
E 29.54890 29.82261 29.91684 31.20166 32.50274 34.73485 35.34467 36.54069
E 37.04201 37.84974 39.19511 40.69464 42.50407 43.69879 44.95288 44.98957
[03] Transferred momenta grid
=============================
IBZ Q-points : 6
BZ Q-points : 32
Q [00001] : 0.000 0.000 0.000 (iku) * weight 0.03125
Q [00002] :-0.500000 0.000000 -0.500000 (iku) * weight 0.375000
Q [00003] :-0.500000 -0.500000 -0.500000 (iku) * weight 0.125000
Q [00004] : 0.000000 -0.500000 0.000000 (iku) * weight 0.187500
Q [00005] :-1.000000 -0.500000 0.000000 (iku) * weight 0.187500
Q [00006] :-1.000000 0.000000 0.000000 (iku) * weight 0.09375
:: Indices: polarization function