I have some questions regarding QP band structure calculations, specifically how the results are reported.
It is my understanding that Yambo shifts the KS energies coming out of in this case Quantum Espresso. For example, QE output is for the first k-point has the highest occupied band at 2.4511eV, and the lowest unoccupied one at 3.223eV. It also reports a Fermi energy of 2.7509eV.
In r_setup I however see a Fermi energy of 2.84eV and at the first k-point energies of -0.391309eV and 0.380611eV (see also CBmin and CBmax) reported here:
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[02.05] Energies & Occupations
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[X] === General ===
[X] Electronic Temperature : 0.258606E-1 300.100 [eV K]
[X] Bosonic Temperature : 0.258606E-1 300.100 [eV K]
[X] Finite Temperature mode : yes
[X] El. density : 0.29601E+24 [cm-3]
[X] Fermi Level : 2.842452 [eV]
[X] === Gaps and Widths ===
[X] Conduction Band Min : 0.341384 [eV]
[X] Valence Band Max : -0.348692 [eV]
[X] Filled Bands : 102
[X] Empty Bands : 103 300
[X] Direct Gap : 0.701256 [eV]
[X] Direct Gap localized at k-point : 9
[X] Indirect Gap : 0.690076 [eV]
[X] Indirect Gap between k-points : 8 10
[X] Last valence band width : 0.349303 [eV]
[X] 1st conduction band width : 0.309158 [eV]
Then, in the resulting *.qp file, also the shifted KS energies show up. With the QP shifts being "asymmetric".
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1 102 -0.391309 -1.192311 -0.593971
1 103 0.380611 0.451979 -3.108466
Addition:
I was also confused by ypp's output. I am running the interpolation in batches. And I notice it reports
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<---> [06.04] Fermi Levels
<---> Fermi Level (BUILT-in bands) : 2.842452 [eV]
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<---> [06.04] Fermi Levels
<---> Fermi Level (BUILT-in bands) : 0.000000 [eV]