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I want to know why we need fake k-points in HSE band structure calculation? I mean why we can't take a simple high symmetric path like we do in PBE calculation?

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  • $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Commented Feb 14, 2022 at 23:51
  • $\begingroup$ +1 and welcome to our new community! Thank you for contributing your question here and we hope to see much more of you in the future !!! $\endgroup$ Commented Feb 14, 2022 at 23:53

2 Answers 2

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The reason is that the HSE method are obtaining the band structure with self-consistent calculation rather than non-self-consistent calculation like PBE band structure calculation. For self-consistent calculation, you will sample the k-space with a uniform k mesh. The fake k-points are just the high-symmetry path used in PBE calculations, which are added into the self-consistent calculations to calculate the eigenvalues or energy band you are wanted.

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  • $\begingroup$ ok so what if I do the HSE calculation in the same manner as we do PBE calculation? Is there any specific advantage or motive to do the HSE calculation in a different manner i.e. the fake k-point procedure. $\endgroup$ Commented Feb 15, 2022 at 8:28
  • $\begingroup$ You can try and see what will happen. $\endgroup$
    – Jack
    Commented Feb 20, 2022 at 14:17
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This question has already been answered in the quantum espresso forum here. To reiterate the Fock operator at a certain k-point needs the wavefunction on a grid that is commensurate with it. Hence we cannot calculate the single k-point non-selfconsistently from the charge density. Therefore, in a hybrid functional we have to use the entire self consistent calculations.

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  • $\begingroup$ Ok I understood what you are trying to say but what if I do a first self consistent calculation(SCF) with HSE tags and I take the WAVECAR of this SCF as you mentioned Fock operator needs the wavefunction on the grid and now with this WAVECAR I do non-SCF calculation with high symmetry K-point path. I know I am adding an extra step but I just want to know will it give the same results? $\endgroup$ Commented Feb 16, 2022 at 19:38

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