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Dear all,

I have a few questions regarding the calculation of Fermi energy in VASP, while doing gamma-point calculations for semiconductors.
1. How is the Fermi energy defined / calculated in VASP?
2. What are the factors that affect the absolute value of Fermi energy?
3. In case of an intrinsic semiconductor, should I expect the Fermi energy to lie exactly at the centre of the band gap?

Any comments are appreciated. Thanks in advance!

1. The energy that returns the correct number of electrons when integrating the bands up to this level with whatever method for Brillouin zone integration that you use.
2. Don't know. This depends of course on the definition of zero potential energy, but this is a fairly arbitrary thing which is probably safest left without interpretation.
3. Nope. This will depend on the BZ integration scheme you use. It should end up at the valence band maximum (that's the HOMO, if you feel like a chemist) when the smearing width goes to zero.