About QP correction

[sdwang]

Dear developers and Yambo users:
I have calculated a semiconductor with direct gap about 3.0eV, and I want to get QP correction.The 14th band is the highest valence band and the 15th is the lowest conduction band in my unit.After GW calculatin , I get
Kpt Band Eo E-Eo Sc(Eo)
1.00000 12.00000 -1.82708 3.43028 0.72235
1.00000 13.00000 -0.99514 5.13049 -1.32342
1.00000 14.0000 0.000 4.541 0.8014
1.00000 15.00000 3.02934 -2.77184 0.35725
1.00000 16.00000 4.20312 -2.61442 1.27998
.....

I list the first k point data. If I sum column3 and column4, I get the GW energy E as following(Is it right?):
E=Eo + E-Eo
1.6032
4.13535
4.5410
0.2575
1.5887
The data corresponds to the band 12-band 16.My question is:
Why the band 13(4.13535eV) and band 14( 4.541eV) higher than band 15 (0.2575eV) and band 16 (1.5887)?

My GW input file is:

gw0 # [R GW] GoWo Quasiparticle energy levels
ppa # [R Xp] Plasmon Pole Approximation
xxvxc # [R XX] Hartree-Fock Self-energy and Vxc
em1d # [R Xd] Dynamical Inverse Dielectric Matrix
FFTGvecs= 3001 RL # [FFT] Plane-waves
EXXRLvcs= 3001 RL # [XX] Exchange RL components
XfnQPdb= "none" # [EXTQP Xd] Database
XfnQP_N= 1 # [EXTQP Xd] Interpolation neighbours
% XfnQP_E
0.000000 | 1.000000 | 1.000000 | # [EXTQP Xd] E parameters (c/v)
%
% QpntsRXp
1 | 14 | # [Xp] Transferred momenta
%
% BndsRnXp
1 | 100 | # [Xp] Polarization function bands
%
NGsBlkXp= 500 RL # [Xp] Response block size
CGrdSpXp= 100.0000 # [Xp] [o/o] Coarse grid controller
% EhEngyXp
-1.000000 |-1.000000 | eV # [Xp] Electron-hole energy range
%
% LongDrXp
1.000000 | 0.000000 | 0.000000 | # [Xp] [cc] Electric Field
%
PPAPntXp= 27.21138 eV # [Xp] PPA imaginary energy
GfnQPdb= "none" # [EXTQP G] Database
GfnQP_N= 1 # [EXTQP G] Interpolation neighbours
% GfnQP_E
0.000000 | 1.000000 | 1.000000 | # [EXTQP G] E parameters (c/v)
%
% GbndRnge
1 | 100 | # [GW] G[W] bands range
%
GDamping= 0.10000 eV # [GW] G[W] damping
QPreport= "kpbne0ees0" # [GW] QP info. Keys: kp/bn/xx/xc/s0/sq/e0/eq/ee/zf/ds/lm/lf
%QPkrange # [GW] QP generalized Kpoint/Band indices
1| 12| 12| 16|
%
%QPerange # [GW] QP generalized Kpoint/Energy indices
1| 12| 0.0|-1.0|
%

[Conor Hogan]

Why the band 13(4.13535eV) and band 14( 4.541eV) higher than band 15 (0.2575eV) and band 16 (1.5887)?

Dear Shudong,

The results do seem a bit strange. Can you tell us more about your system, by adding the report files and pwscf/abinit input files?
It's hard to tell whats going on just from what you show here. Possibly the number of EXXRL is too low - did you check the convergence of the Hartree-Fock gap with the FFT and EXXRl G-vectors?

Regards,
Conor

[sdwang]

Why the band 13(4.13535eV) and band 14( 4.541eV) higher than band 15 (0.2575eV) and band 16 (1.5887)?

Dear Shudong,

The results do seem a bit strange. Can you tell us more about your system, by adding the report files and pwscf/abinit input files?
It's hard to tell whats going on just from what you show here. Possibly the number of EXXRL is too low - did you check the convergence of the Hartree-Fock gap with the FFT and EXXRl G-vectors?

Regards,
Conor

Dear Conor:
How can I check the "convergence of the Hartree-Fock gap with the FFT and EXXRl G-vectors?" I post my input of scf and report.
SDWang

[Daniele Varsano]

Dear Shudong,

How can I check the "convergence of the Hartree-Fock gap with the FFT and EXXRl G-vectors?"

as all the other variables. Add G vectors in your calculation until the result is converged.

Best,
Daniele

[Conor Hogan]

How can I check the "convergence of the Hartree-Fock gap with the FFT and EXXRl G-vectors?"

Do a calculation of the exchange self energy, and look at the difference between <14|Sx|14>-<14|Vxc|14> and <15|Sx|15>-<15|Vxc|15> as the various parameters are increased., especially FFTGvecs and EXXRLvcs. Don't move onto the next steps until you are sure you know what you are doing!

[sdwang]

Thank you! Can you explain the meaning of the following data?
S_x/V_xc [eV] @ K [1] (iku): 0.166667 0.250000 0.000000----------
<12|S_x|12> = -23.91940 0.2578E-7 <12|V_xc|12> = -18.78779 0.5069E-7
<13|S_x|13> = -19.35795 -.1396E-7 <13|V_xc|13> = -16.69009 -.1980E-8
<14|S_x|14> = -24.42550 0.6405E-8 <14|V_xc|14> = -19.48935 -.1584E-7
<15|S_x|15> = -8.202393 0.2274E-9 <15|V_xc|15> = -13.36181 -.8452E-8
<16|S_x|16> = -10.69838 -.1408E-8 <16|V_xc|16> = -16.07968 -.1188E-8
...
For line one, -23.91940 and 0.2578E-7 is what? -18.78779 and 0.5069E-7?and <12|S_x|12>, <12|V_xc|12>??
I kown my quetion is folish, but I realy do not kown that.Thank you for your help me.
SDWang

[Daniele Varsano]

Dear Shudong,
They are respectively the real and imaginary part of the exchange part of the Self energy Sx,
and the real and imaginary part of the exchange and correlation potential Vxc.

I strongly suggest you to study some review on GW calculations before running your
calculations, otherwise you take the big risk to believe results that you don't know how
they are calculated. You can take a look at the documentation as well to the
lecture notes section of the yambo website.
There you can find both slides of lectures and reviews article.

Best,

Daniele

[sdwang]

Thanks! I will study it carefully.

[sdwang]

Dear developers:
I get my qp energy but I find in some k-points, high energy conductin band, their energy are lower than the lowest one( in red colour), does this relate the convergence ??

QP [eV] @ K [4] (iku): 0.240000 0.000000 0.000000
B=31 Eo= -1.09 E= -1.77 E-Eo= -0.68 Z=0.74 So= 2.76970 xx=-18.61768 Vxc=-14.92427
B=32 Eo= -0.65 E= -0.67 E-Eo= -0.02 Z=0.74 So= 3.662 xx=-18.77 Vxc=-15.08
B=33 Eo= -0.57 E= -1.17 E-Eo= -0.60 Z=0.75 So= 2.66896 xx=-18.78436 Vxc=-15.30612
B=34 Eo= -0.18 E= -0.36 E-Eo= -0.18 Z=0.76 So= 3.24371 xx=-19.19191 Vxc=-15.70677
B=35 Eo= 4.32 E= 6.00 E-Eo= 1.68 Z=0.79 So= -2.92511 xx= -5.47215 Vxc=-10.51264
B=36 Eo= 4.56 E= 6.08 E-Eo= 1.52 Z=0.79 So= -3.03574 xx= -5.65218 Vxc=-10.61958
B=37 Eo= 4.85 E= 7.33 E-Eo= 2.48 Z=0.79 So= -2.11877 xx= -6.23477 Vxc=-11.48816
B=38 Eo= 4.93 E= 7.44 E-Eo= 2.51 Z=0.80 So= -2.02549 xx= -6.28761 Vxc=-11.46788

QP [eV] @ K [5] (iku): 0.320000 0.000000 0.000000
B=31 Eo= -1.31 E= -2.01 E-Eo= -0.70 Z=0.74 So= 2.79996 xx=-18.48006 Vxc=-14.72541
B=32 Eo= -0.81 E= -0.96 E-Eo= -0.15 Z=0.74 So= 3.43597 xx=-18.67020 Vxc=-15.03283
B=33 Eo= -0.63 E= -1.13 E-Eo= -0.50 Z=0.75 So= 2.91798 xx=-18.74755 Vxc=-15.15518
B=34 Eo= -0.31 E= -0.52 E-Eo= -0.20 Z=0.75 So= 3.24112 xx=-19.05512 Vxc=-15.54309
B=35 Eo= 4.41 E= 6.09 E-Eo= 1.68 Z=0.79 So= -2.90538 xx= -5.53387 Vxc=-10.55463
B=36 Eo= 4.57 E= 6.21 E-Eo= 1.64 Z=0.79 So= -2.89099 xx= -5.61135 Vxc=-10.58047
B=37 Eo= 5.00 E= 7.36 E-Eo= 2.36 Z=0.79 So= -2.26903 xx= -6.32549 Vxc=-11.58544
B=38 Eo= 5.06 E= 5.78 E-Eo= 0.72 Z=0.88 So=-1.828341 xx=-1.508085 Vxc=-4.148462

QP [eV] @ K [6] (iku): 0.400000 0.000000 0.000000
B=31 Eo= -1.55 E= -2.28 E-Eo= -0.73 Z=0.73 So= 2.83966 xx=-18.35365 Vxc=-14.52163
B=32 Eo= -1.03 E= -1.29 E-Eo= -0.25 Z=0.74 So= 3.33709 xx=-18.51868 Vxc=-14.83841
B=33 Eo= -0.66 E= -1.09 E-Eo= -0.43 Z=0.75 So= 3.05963 xx=-18.78218 Vxc=-15.14175
B=34 Eo= -0.48 E= -0.70 E-Eo= -0.23 Z=0.75 So= 3.24720 xx=-18.91452 Vxc=-15.36528
B=35 Eo= 4.52 E= 6.18 E-Eo= 1.66 Z=0.79 So= -2.90839 xx= -5.58884 Vxc=-10.59134
B=36 Eo= 4.53 E= 6.28 E-Eo= 1.75 Z=0.79 So= -2.76872 xx= -5.57326 Vxc=-10.54673
B=37 Eo= 5.17 E= 5.86 E-Eo= 0.69 Z=0.88 So=-1.872112 xx=-1.514706 Vxc=-4.166135
B=38 Eo= 5.22 E= 7.46 E-Eo= 2.24 Z=0.78 So= -2.39974 xx= -6.37020 Vxc=-11.63510

Most the other points are OK.

Thanks!

[Daniele Varsano]

Dear Shudong,
it looks you have some band crossing. It can happens and it is possible that there is nothing wrong.
I suggest you to plot the band structures, and looks if, even the index of some bands are reversed,
the bands are continous.

Cheers,

Daniele