Bandgap of Si in GW

From VASP Wiki

Description: calculation of the bandgap of Si using various flavours of GW.


To do GW calculations we have to follow a 3-step procedure.

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
6x6x6
 0
G
 6 6 6
 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: obtain DFT virtual orbitals

  • INCAR
ALGO = Exact
NBANDS  = 64
LOPTICS = .TRUE. ; CSHIFT = 0.1
NEDOS = 2000
## you might try
#LPEAD = .TRUE.
</prec>

To quickly find the QP-energy of the highest lying occupied state, try

 grep "     4     " OUTCAR | sort -n -k 3 | tail -1 | awk '{print $3}'

and for the lowest lying unoccupied state,

 grep "     5     " OUTCAR | sort -n -k 3 | head -1 | awk '{print $3}'

Download

Si_bandgap_GW.tgz
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