I try to calculate the band gap using HSE, but couldn't plot the band plot, procedure is as follows. What's the error?
Band structure calculation by using HSE 06 is completed in two steps
1. HSE SCF: for this copy the input files along with CHGCAR and WAVECAR from PBE-scf. Put the HSE tags in INCAR.
2. HSE-B.S:
when hse.scf is completed then copy the four input files along with CHGCAR, WAVECAR and IBZKPTS from HSE-scf to HSE.B.S.
Then go to PBE -band gap directory and open OUTCAR.
Search "k-points in reciprocal lattice”.
Copy those KPOINTS and paste at the bottom of IBZKPTS and rename it as KPOINTS.
The 4rth column of the kpoints copied from OUTCAR should be changed to 0.000.
Refer to to wiki's explanation, particularly the first option where you provide an explicit list of kpoints (so-called "zero weight" method): https://www.vasp.at/wiki/index.php/Band-structure_calculation_using_hybrid_functionals
In your step 2, you must provide a KPOINTS file that is a combination of the IBZKPT and the path you want to do your band structure on. Taking the example from the wiki, consider the following IBZKPT file found from a PBE band structure calculation,
Automatically generated mesh IBZKPT
4
Reciprocal lattice
0.00000 0.00000 0.00000 1
0.33333 0.00000 0.00000 8
0.33333 0.33333 0.00000 6
-0.33333 0.33333 0.00000 12
Next, you must have your path, say from Γ to X,
0.00000000 0.00000000 0.00000000
0.12500000 0.00000000 0.12500000
0.25000000 0.00000000 0.25000000
0.37500000 0.00000000 0.37500000
0.50000000 0.00000000 0.50000000
Now, you combine them into one KPOINT file where the IBZKPT values go first (along with their weights) and the path goes after WITH ZERO WEIGHT,
Explicit k-points list
9
Reciprocal lattice
0.00000 0.00000 0.00000 1
0.33333 0.00000 0.00000 8
0.33333 0.33333 0.00000 6
-0.33333 0.33333 0.00000 12
0.00000000 0.00000000 0.00000000 0
0.12500000 0.00000000 0.12500000 0
0.25000000 0.00000000 0.25000000 0
0.37500000 0.00000000 0.37500000 0
0.50000000 0.00000000 0.50000000 0
Don't forget to change the number of kpoints as (# of IBZKPT kpts)+(# of explicit kpoints)=4+5=9.
When you run the band structure calculation, you will obtain the EIGENVAL file containing the results. However, the values you want are those whose kpoint weights are zero as these correspond to the path you chose. So when you parse the EIGENVAL file, plot only the blocks of data where the number after the kpoint is 0.
Note from wiki: "Warning: The electronic charge density must not be fixed for any hybrid calculation, i.e., never set ICHARG=11!"
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