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Smearing method and Fermi Energy
Posted: Sat Mar 15, 2025 1:39 pm
by tasdiquearman
Can anyone tell me why and how changing the smearing method (Gaussian Smearing vs. Tetrahedron method) gives different values of Fermi energy during DOS calculations in VASP? Also, when Fermi energy is taken as 0 eV in the DOS plot, the proximity of CBM and VBM to the Fermi energy is different in both cases (Gaussian and Tetrahedron). The DOS plots are attached for reference. The calculation is done for Na3V2(PO4)3.
Re: Smearing method and Fermi Energy
Posted: Sun Mar 16, 2025 3:28 pm
by martin.schlipf
The Fermi energy is not deterministic in the gap. It depends on the method that you use. Any value that leads to an integrated DOS of the number of electrons is in principle fine.
That being said, VASP will typically give values at the bottom of the gap. There are a few VASP versions, 6.2 and 6.3 I believe, where that is not the case for the tetrahedron method. Now, there is a deterministic algorithm EFERMI = MIDGAP which will put the Fermi energy in the middle of the bandgap. This is now the recommended default.