gw change the k-point of VBM in 2D semiconductor

[ljzhou86]

Dear Sir

I am doing the g0w0 calculations on a 2D semiconducting materials, while I encountered a problem: the valence band maximum (VBM) of DFT is located on Gamma (0 0 0 ) point, but the gw corrected VBM is at 0.000000 0.208333 0.000000. I am wondering why yambo change the location of VBM? The g0w0 input is as follows:

#
# __ __ _ __ __ ____ U ___ u
# \ \ / / U /"\ U u |" \/ "| u U | __") u \/"_ \/
# \ V / \/ _ \/ \| |\/| |/ \| _ \/ | | | |
# U_|"|_u / ___ \ | | | | | |_) | .-,_| |_| |
# |_| /_/ \_\ |_| |_| |____/ \_)-\___/
# .-,//|(_ \\ >> <<,-,,-. _|| \\_ \\
# \_) (__) (__) (__) (./ \.) (__) (__) (__)
#
#
# GPL Version 4.1.4 Revision 76
# MPI+OpenMP Build
# http://www.yambo-code.org
#
gw0 # [R GW] GoWo Quasiparticle energy levels
ppa # [R Xp] Plasmon Pole Approximation
rim_cut # [R RIM CUT] Coulomb potential
HF_and_locXC # [R XX] Hartree-Fock Self-energy and Vxc
em1d # [R Xd] Dynamical Inverse Dielectric Matrix
X_Threads= 16 # [OPENMP/X] Number of threads for response functions
DIP_Threads= 16 # [OPENMP/X] Number of threads for dipoles
SE_Threads= 16 # [OPENMP/GW] Number of threads for self-energy
RandQpts=3000000
RandGvec= 100 RL # [RIM] Coulomb interaction RS components
CUTGeo= "box z" # [CUT] Coulomb Cutoff geometry: box/cylinder/sphere X/Y/Z/XY..
% CUTBox
0.00 | 0.00 | 65.00 | # [CUT] [au] Box sides
%
CUTRadius= 0.000000 # [CUT] [au] Sphere/Cylinder radius
CUTCylLen= 0.000000 # [CUT] [au] Cylinder length
EXXRLvcs= 10503 RL # [XX] Exchange RL components
Chimod= "Hartree" # [X] IP/Hartree/ALDA/LRC/BSfxc
% BndsRnXp
1 | 300 | # [Xp] Polarization function bands
%
NGsBlkXp= 6 Ry # RL # [Xp] Response block size
% LongDrXp
1.000000 | 0.000000 | 0.000000 | # [Xp] [cc] Electric Field
%
PPAPntXp= 27.21138 eV # [Xp] PPA imaginary energy
% GbndRnge
1 | 300 | # [GW] G[W] bands range
%
GDamping= 0.10000 eV # [GW] G[W] damping
dScStep= 0.10000 eV # [GW] Energy step to evaluate Z factors
DysSolver= "n" # [GW] Dyson Equation solver ("n","s","g")
%QPkrange # [GW] QP generalized Kpoint/Band indices
1| 61| 35|46|
%

I attached the r_* log file for anyone to help me to analyze the problem? Thanks a lot

[Daniele Varsano]

Dear Dr. Zhou Liu-Jiang,

you may want to check your convergences, anyway from your report I can see you have QP energies
E= 0.07 at gamma
E= -0.12 at k=0.000000 0.208333 0.000000

so ~0.2 eV below than the energy at gamma point, i.e very similar to the energy difference you find at KS level (0.22eV).

Best,

Daniele

[ljzhou86]

Dear Dr. Zhou Liu-Jiang,


E= -0.12 at k=0.000000 0.208333 0.000000

so ~0.2 eV below than the energy at gamma point, i.e very similar to the energy difference you find at KS level (0.22eV).

Daniele

Dear Daniele,

How do you get the QP energy of -0.12 at k=0.000000 0.208333 0.000000? Actually, the VBM QP energies is 0.09701 eV at the 40th band, sixth k-point (0.000000 0.208333 0.000000). The QP energy difference is about 0.03 eV eV, while that at KS level is up to 0.22 eV, showing a significant distinction. Can you tell me which parameter usually determine the inconsistency? Thanks a lot

[Daniele Varsano]

Dear Zhou Liu-Jiang,
according to the report you posted:
QP [eV] @ K [6] (iku): 0.000000 0.208333 0.000000
B=35 Eo= -0.98 E= -1.13 E-Eo= -0.15 Re(Z)=0.77 Im(Z)=-.2555E-2 nlXC=-16.13 lXC=-13.91 So= 2.036
B=36 Eo= -0.93 E= -1.08 E-Eo= -0.15 Re(Z)=0.77 Im(Z)=-.2450E-2 nlXC=-16.21 lXC=-14.00 So= 2.025
B=37 Eo= -0.85 E= -1.08 E-Eo= -0.23 Re(Z)=0.78 Im(Z)=-.1807E-2 nlXC=-16.10 lXC=-13.91 So= 1.897
B=38 Eo= -0.78 E= -1.00 E-Eo= -0.22 Re(Z)=0.78 Im(Z)=-.1731E-2 nlXC=-16.23 lXC=-14.05 So= 1.906
B=39 Eo= -0.23 E= -0.13 E-Eo= 0.10 Re(Z)=0.77 Im(Z)=-.2436E-2 nlXC=-16.31 lXC=-14.77 So= 1.664
B=40 Eo= -0.22 E= -0.12 E-Eo= 0.10 Re(Z)=0.77 Im(Z)=-.2422E-2 nlXC=-16.32 lXC=-14.78 So= 1.665

I can see at Band 40:
EKS=-0.22eV
EQP=-0.12eV

Are we looking at the same file?

Best,
Daniele