关注：

1） 实例解读

2） GW算法原理

 http://cms.mpi.univie.ac.at/wiki/index.php/Bandstructure_of_Si_in_GW_(VASP2WANNIER90)

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.

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.

ALGO = Exact

NBANDS  = 64

LOPTICS = .TRUE.

NEDOS = 2000

ISMEAR =  0

SIGMA  =  0.05

GGA    = PE

# ALGO = Exact or  ALGO = Diag performs an exact diagonalization (IALGO = 90), and we recommend to use this if more than 30-50 % of the states are calculated (e.g. for or RPA calculations).

 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
 ........
    0.0000000     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 wannier90.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

Download

Si_bandstructure_GW.tgz

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