Bandstructure of Si in GW (VASP2WANNIER90)
Description: calculation of the bandstructure of Si in GW using the VASP2WANNIER90 interface.
Mind: The procedure to compute bandstructure in GW using V2W is almost identical to the corresponding HSE one described in Si bandstructure.
Mind: The standard procedure for GW calculations is described in bandgap of Si in GW.
Step 1: a DFT groundstate calculation
Everything starts with a standard DFT groundstate calculation (in this case PBE).
- INCAR
ISMEAR = 0 SIGMA = 0.05 GGA = PE
- KPOINTS
4x4x4 0 G 4 4 4 0 0 0
- POSCAR
system Si 5.430 0.5 0.5 0.0 0.0 0.5 0.5 0.5 0.0 0.5 2 cart 0.00 0.00 0.00 0.25 0.25 0.25
Step 2: obtain DFT virtual orbitals
To obtain a WAVECAR file with a reasonable number of virtual orbitals (50-100 per atom) we need to restart from the previous groundstate calculation with ALGO=Exact, and manually set the number of bands by means of the NBANDS-tag. To obtain the corresponding WAVEDER file we additionally specify LOPTICS=.TRUE.
- INCAR
ALGO = Exact NBANDS = 64 LOPTICS = .TRUE. NEDOS = 2000 ISMEAR = 0 SIGMA = 0.05 GGA = PE
Step 3: GW calculation including LWANNIER90 TAG
Restart from the WAVECAR and WAVEDER files of the previous calculation, with
- INCAR
## Frequency dependent dielectric tensor including ## local field effects within the RPA (default) or ## including changes in the DFT xc-potential (LRPA=.FALSE.). ## N.B.: beware one first has to have done a ## calculation with ALGO=Exact and LOPTICS=.TRUE. ## and a reasonable number of virtual states (see above) ALGO = GW0 ; LSPECTRAL = .TRUE. ; NOMEGA = 50 #LRPA = .FALSE. ## be sure to take the same number of bands as for ## the LOPTICS=.TRUE. calculation, otherwise the ## WAVEDER file is not read correctly NBANDS = 64 ##VASP2WANNIER90 LWANNIER90=.TRUE.
Use the wannier90.win file given below which contains all instructions needed to generate the necessary input files for the WANNIER90 runs (wannier90.amn, wannier90.mmn, wannier90.eig).
- wannier90.win
num_wann=8
num_bands=8
exclude_bands 9-64
Begin Projections
Si:sp3
End Projections
dis_froz_max=9
dis_num_iter=1000
guiding_centres=true
# Bandstructure plot
#restart = plot
#bands_plot = true
#begin kpoint_path
#L 0.50000 0.50000 0.5000 G 0.00000 0.00000 0.0000
#G 0.00000 0.00000 0.0000 X 0.50000 0.00000 0.5000
#X 0.50000 0.00000 0.5000 K 0.37500 -0.37500 0.0000
#K 0.37500 -0.37500 0.0000 G 0.00000 0.00000 0.0000
#end kpoint_path
#bands_num_points 40
#bands_plot_format gnuplot xmgrace
begin unit_cell_cart
2.7150000 2.7150000 0.0000000
0.0000000 2.7150000 2.7150000
2.7150000 0.0000000 2.7150000
end unit_cell_cart
begin atoms_cart
Si 0.0000000 0.0000000 0.0000000
Si 1.3575000 1.3575000 1.3575000
end atoms_cart
mp_grid = 4 4 4
begin kpoints
0.0000000 0.0000000 0.0000000
0.2500000 0.0000000 0.0000000
0.5000000 0.0000000 0.0000000
0.2500000 0.2500000 0.0000000
0.5000000 0.2500000 0.0000000
-0.2500000 0.2500000 0.0000000
0.5000000 0.5000000 0.0000000
-0.2500000 0.5000000 0.2500000
0.0000000 0.2500000 0.0000000
0.0000000 0.0000000 0.2500000
-0.2500000 -0.2500000 -0.2500000
-0.2500000 0.0000000 0.0000000
0.0000000 -0.2500000 0.0000000
0.0000000 0.0000000 -0.2500000
0.2500000 0.2500000 0.2500000
0.0000000 0.5000000 0.0000000
0.0000000 0.0000000 0.5000000
-0.5000000 -0.5000000 -0.5000000
0.0000000 0.2500000 0.2500000
0.2500000 0.0000000 0.2500000
-0.2500000 -0.2500000 0.0000000
-0.2500000 0.0000000 -0.2500000
0.0000000 -0.2500000 -0.2500000
0.0000000 0.5000000 0.2500000
0.2500000 0.0000000 0.5000000
-0.2500000 -0.2500000 0.2500000
-0.5000000 -0.2500000 -0.5000000
0.2500000 0.5000000 0.0000000
0.2500000 -0.2500000 -0.2500000
-0.5000000 -0.5000000 -0.2500000
0.0000000 0.2500000 0.5000000
-0.2500000 0.2500000 -0.2500000
-0.2500000 -0.5000000 -0.5000000
0.5000000 0.0000000 0.2500000
-0.5000000 -0.2500000 0.0000000
0.0000000 -0.5000000 -0.2500000
-0.2500000 0.0000000 -0.5000000
0.2500000 0.2500000 -0.2500000
0.5000000 0.2500000 0.5000000
-0.2500000 -0.5000000 0.0000000
-0.2500000 0.2500000 0.2500000
0.5000000 0.5000000 0.2500000
0.0000000 -0.2500000 -0.5000000
0.2500000 -0.2500000 0.2500000
0.2500000 0.5000000 0.5000000
-0.5000000 0.0000000 -0.2500000
0.0000000 -0.2500000 0.2500000
0.2500000 0.0000000 -0.2500000
-0.2500000 -0.2500000 -0.5000000
0.2500000 0.5000000 0.2500000
0.2500000 -0.2500000 0.0000000
-0.5000000 -0.2500000 -0.2500000
0.2500000 0.2500000 0.5000000
0.0000000 0.2500000 -0.2500000
-0.2500000 -0.5000000 -0.2500000
0.5000000 0.2500000 0.2500000
-0.2500000 0.0000000 0.2500000
0.0000000 0.5000000 0.5000000
0.5000000 0.0000000 0.5000000
0.2500000 -0.2500000 0.5000000
0.5000000 0.2500000 -0.2500000
-0.5000000 -0.2500000 -0.7500000
0.2500000 -0.5000000 -0.2500000
-0.2500000 0.2500000 -0.5000000
end kpoints
Step 4: WANNIER90
Compute Wannier functions
run wannier90:
wannier90.x wannier90
This run generates the wannier90 standard output (wannier90.wout) and the file wannier90.chk needed for the wannier interpolation (next step)
Obtain bandstructure (Wannier interpolation)
Uncomment the bandstructure plot flags in wannier.win and rerun (restart) wannier90:
wannier90.x wannier90
This run generates the following bandstructure files which can be visualized using xmgrace or gnuplot:
wannier90_band.agr
wannier90_band.dat
wannier90_band.gnu
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