Fermi Energy in insulator/semiconductor

Posted on : October 22, 2021 (Fri) 02:38:04

by Yohanes Pramudya

I have difficulty understanding the DOS because the Fermi energy is generally not right from the output file. Often The Fermi energy is not in the gap for insulators or semiconductors like BaTiO3 or SrTiO3. The DOS looks fine but the position of Fermi Energy is often confusing. Do we have any guidance how to read the output of the DOS matching with the Fermi Energy? I think the Fermi energy is somehow shifted.

[Re:02] Fermi Energy in insulator/semiconductor

Posted on : November 30, 2021 (Tue) 00:16:55

by Yohanes Pramudya

Thanks Hitoshi,

My concern is not to place the Fermi energy in between VBM and CBM but often the Fermi energy is completely misplaced. We may find an insulator is predicted to be metal if the Fermi energy is not right. As I understand, AKAI-KKR does not apply Lloyd-Formula in the calculation for finding the Fermi energy reliably in insulator materials.

[Re:01] Fermi Energy in insulator/semiconductor

Posted on : October 22, 2021 (Fri) 17:54:17

by Hitoshi GOMI

Hello Yohanes Pramudya,

That is normal behavior.
I'm not a developer, so this may not be correct, but here's what I understand.

The Fermi energy is calculated by integrating the states from the bottom of the ewidth.
Since there are no states within the band gap, I think it is difficult to set the center of the band gap as the Fermi energy via the numerical integration.

Perhaps if you decrease the edelt and increase the bzqlty, you will see an improvement.
However, I do not know if the result will be satisfactory to you.

If you want to plot a DOS relative to the VBM or the Fermi energy, read the VBM and/or CBM from the calculation of the Bloch spectral function and shift the energy accordingly.

Hitoshi GOMI