EFERMI: Difference between revisions

Revision as of 13:00, 30 March 2022

EFERMI = MIDGAP | LEGACY | [real]
Default: EFERMI = MIDGAP

Description: Defines how the Fermi energy is calculated in VASP.

For semiconducting materials, the Fermi energy is not uniquely defined in the bandgap of the material. Any value that produces the correct number of electrons is allowed. By default, VASP will put the Fermi energy in the middle of the gap because this is the most consistent with increasing the smearing SIGMA. This algorithm to determine the Fermi energy was introduced in VASP.6.4.

For prior versions, VASP places the Fermi energy at a somewhat arbitrary value within the bandgap. The precise value depends on values chosen for the smearing (ISMEAR and SIGMA) and the density of states (EMIN, EMAX, and NEDOS). Typically this places the Fermi energy towards the bottom of the bandgap. The value of the Fermi energy should not affect the outcome of the calculation but you can recover the old behavior set EFERMI = LEGACY.

Enforce a particular value for the Fermi energy by setting it to a numeric value. Note that this may change the number of electrons.

Related Tags and Sections

ISMEAR, SIGMA, EMIN, EMAX, NEDOS

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 The value of the Fermi energy should not affect the outcome of the calculation but you can recover the old behavior set {{TAG|EFERMI}} = LEGACY.
-Enforce a particular value for the Fermi energy exhibits by setting it to a numeric value.
+Enforce a particular value for the Fermi energy by setting it to a numeric value.
 Note that this may change the number of electrons.