band gap of RbGeCl3 using GW

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new_986
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band gap of RbGeCl3 using GW

Post by new_986 » Thu Jul 16, 2020 3:45 pm

Dear all
Greetings...
I am trying to calculate band gap of cubic perovskite RbGeCl3.
The value of the band gap changes with the change of the number of bands used in the computation of Eigen functions and Eigen values (dataset 2),
How I know what the correct number of bands

my Input:

ndtset 4

gwcalctyp 20
#paral_kgb 1
gwmem 0
gwpara 2
paral_atom 1

occopt 1
tsmear 0.002

ngkpt 4 4 4

nshiftk 1
shiftk 1 1 1
istwfk *1
tolwfr 1.0d-10

# Dataset1: usual self-consistent ground-state calculation
# Definition of the k-point grid
shiftk1 1 1 1
istwfk1 *0
tolvrs1 1e-10
prtcif1 1
# Dataset2: calculation of WFK file
# Definition of k-points
iscf2 -2
getden2 -1
nband2 105
nbdbuf2 10
localrdwf 1
# Dataset3: Calculation of the screening (epsilon^-1 matrix)
optdriver3 3 # Screening calculation
getwfk3 -1 # Obtain WFK file from previous dataset
nband3 40 # Bands to be used in the screening calculation
ecutwfn3 30 # Planewaves to be used to represent the wavefunctions

ecuteps3 40

ppmfrq3 16.7 eV # Imaginary frequency where to calculate the screening


# Dataset4: Calculation of the Self-Energy matrix elements (GW corrections)
optdriver4 4 # Self-Energy calculation
getwfk4 -2 # Obtain WFK file from dataset 1
getscr4 -1 # Obtain SCR file from previous dataset
nband4 40 # Bands to be used in the Self-Energy calculation
ecutwfn4 30
ecutsigx4 40

nkptgw4 1
kptgw4 0.5 0.5 0.5

bdgw4 22 23


# Definition of the unit cell: fcc
acell 3*5.289805273 Angstr
rprim 1 0 0
0 1 0
0 0 1

# Definition of the atom types
ntypat 3
znucl 37 32 17


# Definition of the atoms
natom 5
typat 1 2 3 3 3
xred 4.0572364839E-29 3.8216794882E-30 -2.0266486347E-29
5.0000000000E-01 5.0000000000E-01 5.0000000000E-01
5.0000000000E-01 5.0000000000E-01 -2.0266486347E-29
5.0000000000E-01 3.8216794882E-30 5.0000000000E-01
4.0572364839E-29 5.0000000000E-01 5.0000000000E-01


# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 45
ecutsm 0.5


# Definition of the SCF procedure
nstep 200
diemac 8

symmorphi 0


any help please?

Thanks in advance
Nawzad

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