GW Band Structure Plots

GW Band Structure Plots

ZZ:http://www.quantumquibbles.com/blog/

To obtain band structure plots from the GW method, first you have to perform a DFT calculation. The INCAR file I used for DFT on Si looks like this:

ISTART = 0
ISYM = 0
ICHARG = 2
ISMEAR = 0
SIGMA = 0.1
LORBIT = 11
NSW = 200
IBRION = 2
ISIF = 3
EDIFF = 0.0001
EDIFFG = -0.01


KPOINTS file for the run is:

Monkhorst Pack
0
Gamma
4 4 4
0 0 0

POSCAR file is:

Si
5.38936000000000
0.5000000000000000 0.5000000000000000 0.0000000000000000
0.0000000000000000 0.5000000000000000 0.5000000000000000
0.5000000000000000 0.0000000000000000 0.5000000000000000
2
Direct
0.0000000000000000 0.0000000000000000 0.0000000000000000
0.2500000000000000 0.2500000000000000 0.2500000000000000

POTCAR file is supplied with VASP 5.2, remember to use paw pseudopotentials so that in the band structure calculation the Wigner-Seitz radius for Si need not be directly specified in INCAR.

After this run completes you are ready to perform the HF-type (HSE06) calculation. Change the INCAR file to:

ISTART = 1
ICHARG = 2
EDIFF = 0.0001
EDIFFG = -0.01
ENCUT = 400
ENAUG = 800
LREAL = .FALSE.
LWAVE = .TRUE.
LCHARG = .TRUE.
NELM = 200
NSW = 0
IBRION = -1
LMAXMIX = 4
ISMEAR = 0
SIGMA = 0.1
NSIM = 4
IALGO = 48
ISYM = 0
LHFCALC = .TRUE.
HFSCREEN = 0.2
ALGO = Damped
TIME = 0.4
ENCUTFOCK = 0
NKRED = 2
AEXX = 0.25

Keep the other files constant for this run (e.g. KPOINTS, POSCAR, POTCAR need not be changed).

Once this run has completed, add to the bottom of the INCAR file from the HSE06 calculation:

LOPTICS = .TRUE.

This step calculates the dielectric matrix

Once this run has completed, change

ALGO = Damped

to

ALGO = GWo

and

ICHARG = 2

to

ICHARG = 11

and add:

NOMEGA = 50
ENCUTGW = 100
LORBIT = 11

and change the KPOINTS file to:

k-points along high symmetry lines
20 ! 20 intersections
Line-mode
rec
0 0 0 ! gamma
0.5 0.0 0 ! X
0.5 0.0 0 ! X
0.5 0.5 0.0 ! M
0.5 0.5 0.0 ! M
0.0 0.0 0.0 ! gamma
0.0 0.0 0.0 ! gamma
0.5 0.5 0.0 ! M
0.5 0.5 0.0 ! M
0.5 0.5 0.5 ! R
0.5 0.5 0.5 ! R
0.0 0.0 0.0 ! gamma

These values are the points of high symmetry along the lines of high symmetry within the first Brillouin Zone of the Si unit cell structure in reciprocal space. And that’s it! Once complete you can plot the PROCAR, EIGENVAL, and DOSCAR files from the output of this run as described in the previous posts. The band structure plot produced from the plotting utility is shown below.