4 Steps:
Structural relaxation (cell and atoms) --> generate CONTCAR needed for steps 2 - 4
Single-point self-consistency (SCF) calculation --> generate CHGCAR for steps 3 and 4
DOS calculation
Band structure calculation
Step 1: Structural relaxation
After obtaining the output files, use the CONTCAR file as the new POSCAR for steps 2-4.
CONTCAR contains the new relaxed structure of Si FCC
Step 2: Single-point self-consistency calculations
Use the relaxed CONTCAR structure for POSCAR
INCAR settings edits: No ionic relaxation and EDIFF for higher precision results in convergence
Key outputs: CHGCAR and WAVECAR
WAVECAR: Wave function --> Copy to Step 3 DOS
CHGCAR: Charge density --> Copy to Step 3 DOS
Step 3: DOS calculations
Use CHGCAR and WAVECAR output from Step 2
INCAR edits: Don't start from scratch, so ISTART = 1
ICHARG = 11 to read charge density from the CHGCAR file in the directory instead
ISMEAR stick to -5 for the tetrahedron method, which is especially suitable for DOS calculations
Set LORBIT = 11 to output DOSCAR and PROCAR (which is partial DOS); 10 means spdf orbitals, 11 means s, px, py,pz... orbitals (l and m partial DOS)
NEDOS = 1000 for the number of points of DOS
EMIN and EMAX for energy range of DOS
NBANDS for number of bands
Both E range and NBANDS can be obtained in OUTCAR or EIGENVAL of scf calculations; but this can be neglected for VASP to take default values; refer below on how to get from EIGENVAL
KPOINTS: Stick to 21 21 21
POSCAR: Stick to the same relaxed structure
fcc Si
8 286 8
0.0000000E+00 0.0000000E+00 0.0000000E+00 0.1079797E-03
1 -6.194068 1.000000
2 5.643200 1.000000
3 5.643217 1.000000
4 5.643217 1.000000
5 8.203201 0.000000
6 8.203218 0.000000
7 8.203218 0.000000
8 8.783224 0.000000
This means there are 8 bands and 286 kpoints
And each segment consists of 8 bands for each kpoint ...
Step 4: Band structure calculations
Use CHGCAR from step 3; can use WAVECAR from step 2 too (or step 3 as well?)
INCAR edits:
ICHARG = 11 to read from ICHARG file
LORBIT = 11 for both partial and full DOS
KPOINTS edits: Cannot use uniform grid of kpoints but have to specify kpoints path
k-points for bandstructure L-G-X-U K-G 10
line
reciprocal
0.50000 0.50000 0.50000 1 0.00000 0.00000 0.00000 1
0.00000 0.00000 0.00000 1 0.00000 0.50000 0.50000 1
0.00000 0.50000 0.50000 1 0.25000 0.62500 0.62500 1
0.37500 0.7500 0.37500 1 0.00000 0.00000 0.00000 1
10 means 10 points between each line
First line is L to G, then G to X, then X to U, then K to G
All points with weight 1
Need to understand KPOINTS more fundamentally...