the physical definition of the Fermi level in band structure calculation

[beauyy]

What is the physical definition of the Fermi level in band structure calculation? Can I use the relative distance from CBM and VBM to the Fermi level to  estimate the conduction type or doping type ?

[Petr Khomyakov]

If one uses the Fermi-Dirac smearing (not MP or others) for an SCF calculation, the position of the Fermi level is physical, and one can then see whether a semiconductor is intrinsic or doped by looking at the CBM or VBM position with respect to the Fermi level.

[beauyy]

Is it accurate to calculate the position of the Fermi level by ATK-DFT: LCAO? Typically DFT codes fail to accurately define the Fermi level position which can actually be placed anywhere within the gap.

[Petr Khomyakov]

This is exactly what my previous post is about that one can define the physical position of the Fermi level when using the Fermi Dirac broadening method available in QuantumATK for DFT calculations for a given electronic temperature, which acts a broadening/smearing parameter in SCF electronic structure calculations, see the manual https://docs.quantumatk.com/manual/Types/FermiDirac/FermiDirac.html for more details.