QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: beauyy on May 21, 2020, 13:46

Title: the physical definition of the Fermi level in band structure calculation
Post by: beauyy on May 21, 2020, 13:46

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 ?

Title: Re: the physical definition of the Fermi level in band structure calculation
Post by: Petr Khomyakov on May 21, 2020, 16:13

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.

Title: Re: the physical definition of the Fermi level in band structure calculation
Post by: beauyy on May 23, 2020, 03:57

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.

Title: Re: the physical definition of the Fermi level in band structure calculation
Post by: Petr Khomyakov on May 24, 2020, 15:46

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.