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Dear all,
After GW calculations, I find that the band reordering happens. QP energies do not arrange from small to larhe values, please see the datas below.
" QP [eV] @ K [1] (iku): 0.000000 0.000000 0.000000
B=23 Eo= -3.67 E= -4.85 E-Eo= -1.19 Re(Z)=0.77 Im(Z)=-0.175143E-2 nlXC= -22.3558 lXC= -17.3087 So= 3.50469
B=24 Eo= -3.53 E= -4.95 E-Eo= -1.42 Re(Z)=0.78 Im(Z)=-0.180935E-2 nlXC= -18.9270 lXC= -14.4768 So= 2.62507
B=25 Eo= -3.39 E= -4.46 E-Eo= -1.08 Re(Z)=0.76 Im(Z)=-0.204829E-2 nlXC= -21.4974 lXC= -16.8472 So= 3.24276
B=26 Eo= -3.20 E= -3.98 E-Eo= -0.78 Re(Z)=0.76 Im(Z)=-0.128012E-2 nlXC= -25.7508 lXC= -20.6486 So= 4.08062
B=27 Eo= -3.16 E= -3.95 E-Eo= -0.79 Re(Z)=0.75 Im(Z)=-0.164479E-2 nlXC= -22.8949 lXC= -18.2940 So= 3.54895
B=28 Eo= -3.15 E= -4.36 E-Eo= -1.21 Re(Z)=0.77 Im(Z)=-0.228981E-2 nlXC= -20.3397 lXC= -15.8849 So= 2.88288
B=29 Eo= -3.03 E= -4.29 E-Eo= -1.25 Re(Z)=0.77 Im(Z)=-0.266109E-2 nlXC= -19.9514 lXC= -15.5141 So= 2.81835
B=30 Eo= -2.62 E= -3.61 E-Eo= -0.99 Re(Z)=0.77 Im(Z)=-0.154539E-2 nlXC= -21.6207 lXC= -17.4401 So= 2.89157
B=31 Eo= -2.58 E= -3.77 E-Eo= -1.19 Re(Z)=0.77 Im(Z)=-0.160203E-2 nlXC= -21.7075 lXC= -17.1022 So= 3.07256
B=32 Eo= -2.54 E= -4.06 E-Eo= -1.53 Re(Z)=0.78 Im(Z)=-0.189234E-2 nlXC= -18.9362 lXC= -14.4673 So= 2.51086
B=33 Eo= -0.60 E= -1.47 E-Eo= -0.86 Re(Z)=0.79 Im(Z)=-0.129513E-2 nlXC= -16.8764 lXC= -15.3108 So= 0.470181
B=34 Eo= 0.58 E= 1.85 E-Eo= 1.27 Re(Z)=0.79 Im(Z)=-0.647037E-3 nlXC= -10.2084 lXC= -15.7727 So= -3.96542
B=35 Eo= 0.68 E= 1.78 E-Eo= 1.10 Re(Z)=0.79 Im(Z)=-0.816401E-3 nlXC= -10.8965 lXC= -15.7636 So= -3.47564
B=36 Eo= 1.36 E= 2.57 E-Eo= 1.22 Re(Z)=0.79 Im(Z)=-0.103515E-2 nlXC= -10.7124 lXC= -16.2772 So= -4.01906
B=37 Eo= 1.37 E= 2.68 E-Eo= 1.32 Re(Z)=0.78 Im(Z)=-0.193752E-3 nlXC= -10.5697 lXC= -16.6548 So= -4.40572
B=38 Eo= 2.36 E= 3.64 E-Eo= 1.28 Re(Z)=0.78 Im(Z)=-0.862395E-3 nlXC= -12.4788 lXC= -17.1807 So= -3.06701
B=39 Eo= 2.94 E= 4.25 E-Eo= 1.31 Re(Z)=0.79 Im(Z)=-0.138356E-2 nlXC= -10.9602 lXC= -16.8434 So= -4.21473
B=40 Eo= 3.30 E= 4.52 E-Eo= 1.22 Re(Z)=0.81 Im(Z)=-0.104612E-2 nlXC= -9.25290 lXC= -14.4277 So= -3.67791
B=41 Eo= 3.33 E= 4.59 E-Eo= 1.26 Re(Z)=0.79 Im(Z)=-0.168195E-2 nlXC= -10.3271 lXC= -16.3379 So= -4.40285
B=42 Eo= 3.71 E= 5.13 E-Eo= 1.41 Re(Z)=0.80 Im(Z)=-0.940186E-3 nlXC= -10.9999 lXC= -16.7924 So= -4.02613
B=43 Eo= 4.93 E= 5.64 E-Eo= 0.70 Re(Z)=0.87 Im(Z)=-0.119524E-2 nlXC= -3.88729 lXC= -7.12407 So= -2.42761
B=44 Eo= 5.01 E= 5.43 E-Eo= 0.42 Re(Z)=0.91 Im(Z)=-0.774684E-3 nlXC= -1.09512 lXC= -3.02463 So= -1.46755"
What does it mean? Do I need to correct it?
And, the interpolated band stuctures by ypp shows mussy characteristic at some K points? Does it have relationship with the band reordering?
Thanks in advance.

Dear Yimin Ding,

band ordering is maintained according to the KS energies. GW corrections can lead to different correction and hence a different ordering of the bands. This usually happens when bands have different character (localization).
About band interpolation, please post your ypp.in file and we will have a look.
Best,
Daniele

Dear Daniele,
Thanks for your reply.
Please see the attachment.
Beat,

Dear Yimin,

you can try to change the value of INTERP_Shell_Fac and see if the interpolation improves.
Unfortunately, there is not a rule of thumb for this parameter. Just try to play with it and see if you get a less noisy band structure.

If this is not the case, you can resort to wannier interpolation, this is a bit more laborious, but accuracy should increase.
Here is a guide for that:
viewtopic.php?f=9&t=1358&p=6528&hilit=Wannier#p6494
in the post there are links to tutorial and examples.

Best,
Daniele