[Pw_forum] Germanium bulk band structure

[Michael Schofield]

Dear sir/madam,

I am trying to calculate the bulk band structure for Germanium using GGA
exchange-correlation with PAW basis, but the band gap is coming out to be
almost zero. I know DFT underestimates the band gap but it is coming almost
zero (~0.03eV). Is there any means by which I can get more accurate band
gap.

My input script is here:


&control
 calculation = 'nscf',
 verbosity = 'high',
 restart_mode = 'from_scratch',
 prefix = 'Ge_bulk_nscf',
 tstress = .false.,
 tprnfor = .false.,
 pseudo_dir = '/home/Software/QE/pseudopotentials/upf_files/',
 outdir = './output/'
/

&system
 ibrav=2,
 celldm(1) = 10.690937,
 nat=2, ntyp=1,
 nbnd = 12,
 ecutwfc=60,
 ecutrho= 600,
/

&electrons
 diagonalization='david',
 mixing_mode = 'plain',
 mixing_beta = 0.7,
 conv_thr =  1.0d-6,
 electron_maxstep = 500,
/

ATOMIC_SPECIES
 Ge 72.640000 Ge.pbe-kjpaw.UPF

ATOMIC_POSITIONS crystal
 Ge 0.000000 0.000000 0.000000
 Ge 0.250000 0.250000 0.250000

K_POINTS crystal_b
6
0.0   0.0    0.0   100
0.0   0.5    0.0   100
0.0   0.375 -0.375 100
-0.25 0.25  -0.5   100
-0.5  0.0   -0.5   100
0.0   0.0    0.0   1
 -----------------------------------------------------------------
PFA the band structure I am getting from it.

Any help/suggestions will be helpful.




Thanks
Priyank
Dept. of EE
IIT Kanpur, India
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