fermi energy shift on different kpoints

Message

Yue-Wen Fang · #1 Post by **Yue-Wen Fang** » Wed Jun 12, 2013 7:33 am

dear vasp users,

i have two urgent problems.
One is that, when i make scf calculation of LAO/STO superlattice for different kmesh, they got different fermi levers as well as the total energy.
below is some results.
12?8?1 TOTEN = -348.979566 eV E-fermi : 4.7215
12?8?2 TOTEN = -348.98343746 eV E-fermi : 4.7500
12?8?4 TOTEN = -347.52711583 eV E-fermi : 7.3118
other parameters in INCAR are all same. it's very strange they are so different, so i cannot belive in them.

The other question is that, after scf calculation on 12*8*2, i make a dos calculation, and find that the fermi energy is shifted from 4.7500 in scf to 7.4184 in dos. i also ploted the density of state in scf and dos calculation, former states insulator and latter is a metal phase. so ridiculous.

I have check the link http://cms.mpi.univie.ac.at/vasp-forum/ ... p?4.6159.0 related to this question, but it didn't work for me.

#2 Post by **admin** » Wed Jul 03, 2013 11:26 am

the Fermi level is calculated from the KS-level energy of the highest occupied state. Therefore, it may differ if the k-points differ for different k-meshes.
For the DOS-calculation: there seems to be a gap and the lower-most conduction band level seems to be just partly-filled in the DOS calculation. Please have a look at DOSCAR at which energy the integrated DOS equals the number of valence electrons of your system.
This is all one can guess based on the information you give above.