I used qe 6.1.0 and yambo 4.4.0 to do GW+BSE@PBE0. When doing BSE calculation, I encountered the problem that BSE spectra differed a lot in the following two cases:
1. yambo reading ndb.QP for GW+BSE;
2. using scissor operator that is obtained by subtracting QP correction of VBM from QP correction of CBM, e.g., KfnQP_up_E = QPC(CBM_up) – QPC(VBM_up), KfnQP_dn_E = QPC(CBM_dn) – QPC(VBM_dn), where QPC stands for quasi-particle correction.
In looking for the possible issues that caused the problem, I found that yambo switched the spin up and spin down QP energies in BSE calculation from BSE report and BSE output.
For example, in terms of the triplet state system I am doing, from GW calculation output "o-all_Bz.qp" I get
Code: Select all
# K-point Band Eo E-Eo Sc|Eo Spin_Pol
1.0000 145.0000 -3.8606 0.8036 2.2319 1.0000
1.0000 145.0000 -3.7895 0.7925 2.2186 -1.0000
1.0000 146.0000 -2.2941 1.1091 2.1889 1.0000
1.0000 146.0000 2.4610 1.1303 -1.8933 -1.0000
1.0000 147.0000 -2.0422 0.9186 1.7527 1.0000
1.0000 147.0000 2.7222 1.5460 -2.2168 -1.0000
1.0000 148.0000 2.0419 1.1566 -1.5933 1.0000
1.0000 148.0000 3.0862 0.8122 -1.4614 -1.0000
Code: Select all
Then KfnQP_up_E = 1.1566 - 0.9186 = 0.2380 eV and KfnQP_dn_E = 1.1303 - 0.7925 = 0.3378 eV.
Code: Select all
[05.01] External/Internal QP corrections
========================================
...
= FIT report for E<./all_Bz/ndb.QP[ E-E PPA E-E PPA: 27.21138 XG: 7591 Xb: 1 1000 Scb: 1 1000] =
= First column (conduction), Second column (valence) =
= Spin DN ============================================
Gap correction (database) [ev]: 0.234857
(FIT, actual) [ev]: 0.06039
Energies 0th order [ev]: 1.316240 1.020997
Energies 1st order : 0.881223 1.124789
Error: 0.0528 0.0071
= Spin UP ============================================
Gap correction (database) [ev]: 0.338145
(FIT, actual) [ev]: -0.0037
Energies 0th order [ev]: 1.164239 0.829788
Energies 1st order : 0.828994 1.561357
Error: 0.04216 0.05219
Code: Select all
# Eo [eV] DeltaE [eV]
-3.789545 0.792506
2.460562 1.131596
Please kindly take a look at this problem. Thank you.
Best regards,
Kejun