Dear all,

we performed G0W0 calculations starting form a PBE KS system for cubic ZnS. The direct band gaps are 2.00 (PBE), 2.77 (ppa), and 3.33 (cohsex) eV. Our G0W0 results are obviously underestimated with respect to other G0W0 ones reported in the literatures. For instance, the ppa G0W0 result is around 3.5 eV. We increased the density of the k-mesh and the number of the energy bands. However, the underestimate becomes even large. The same underestimate was found in the case of cubic ZnSe. Should we start our G0W0 calcultions from PBE+U KS systems? The following is the input file we used to carry out the G0W0 calculation. It will be appreciated very much if someone gives us some instructions. Thank you, very much.

input file

ndtset 3

# Definition of parameters for the calculation of the KSS file

nbandkss1 -1 # Number of bands in KSS file (-1 means the maximum possible)

nband1 75 # Number of (occ and empty) bands to be computed

kssform1 3

istwfk1 47*1

# Calculation of the screening (epsilon^-1 matrix)

optdriver2 3 # Screening calculation

getkss2 1 # Obtain KSS file from previous dataset

nband2 70 # Bands to be used in the screening calculation

npweps2 169

npwwfn2 169

#ppmfrq2 16.7 eV # Imaginary frequency where to calculate the screening

gwcalctyp2 = 9

#gwcomp2 1

#gwencomp2 1.0

# Calculation of the Self-Energy matrix elements (GW corrections)

optdriver3 4 # Self-Energy calculation

getkss3 1 # Obtain KSS file from dataset 1

getscr3 2 # Obtain SCR file from previous dataset

gwcalctyp3 = 8

nband3 70 # Bands to be used in the Self-Energy calculation

npwsigx3 169

npwwfn3 169

#gwcomp3 1

#gwencomp3 1.0

# Data common to the three different datasets

# Definition of the unit cell: fcc

acell 3*1 Angstrom

rprim -0.000000000000002 2.702649999999999 2.702650000000001

2.702649999999999 -0.000000000000001 2.702650000000001

2.702649999999999 2.702650000000000 0.000000000000001

# Definition of the atom types

ntypat 2

znucl 16 30

# Definition of the atoms

natom 2

typat 1 2

xred

0.25 0.25 0.25

0.00 0.00 0.00

# Definition of the k-point grid

kptopt 1 # Option for the automatic generation of k points,

nkpt 47

ngkpt 10 10 10

nshiftk 1

shiftk 0.0 0.0 0.0 # These shifts will be the same for all grids

istwfk 47*1 # This is mandatory in all the GW steps.

# Use only symmorphic operations

symmorphi 0

ecut 35.0

# Definition of the SCF procedure

nstep 10000

ixc 11

toldfe 1.0d-8

diemac 12.0

#Common to all model GW calculations

nkptgw 1

kptgw

0.00000000E+00 0.00000000E+00 0.00000000E+00

bdgw

9 10

# This line added when defaults were changed (v5.3) to keep the previous, old behaviour

iscf 5

## Our G0W0 results are obviously underestimated

**Moderators:** gmatteo, bruneval, rigna

### Re: Our G0W0 results are obviously underestimated

Does your pseudopotential for Zn consider 3s and 3p electrons as valence ? This is of the utmost importance for the final result.

It has been published several times that G0W0 for ZnO, ZnS, and ZnSe underestimates quite much the experimental band gap. You may turn to self-consistent GW to improve the agreement.

Good luck.

Fabien

It has been published several times that G0W0 for ZnO, ZnS, and ZnSe underestimates quite much the experimental band gap. You may turn to self-consistent GW to improve the agreement.

Good luck.

Fabien