[QE-users] Bi2Se3 vc-relax and band structure calculation

[Varrick Suezaki]

Dear PW users,
I'm trying to do a band structure calculation for bi2se3, but the resulting
band structure does not look like other DFT calculations as it is missing
the 0.3eV band gap.  I also tried uploading my input file to SeeK-Path and
the crystal structure looked wrong and deformed.  Below are my vc-relax and
band input files, is there something I'm missing? I'm using v6.5 on a
CentOS 8 Vmware workstation (Sorry, new to DFT calculations).

&control
calculation = 'vc-relax'
prefix='bi2se3rel'
restart_mode = 'from_scratch'
outdir= '/home/name/QEoutput'
pseudo_dir='/home/name/quantum_espresso/q-e-qe-6.5/pseudo'
etot_conv_thr = 1e-7
forc_conv_thr = 1e-6
/
&system
ibrav = -5, celldm(1) = 18.6947, celldm(4) = 0.9135, nat = 5, ntyp = 3,
ecutwfc = 40, ecutrho = 500,
rhombohedral = .true.,
noncolin=.true.,lspinorb=.true.,starting_magnetization=0.,
nbnd=78,
vdw_corr = 'grimme-d2'
/
&electrons
conv_thr = 1.0e-9,
/
&ions
/
&cell
cell_dofree='ibrav'
/
ATOMIC_SPECIES
 Bi   208.98  Bi.rel-pbe-dn-rrkjus_psl.1.0.0.UPF
 Se1  78.96   Se.rel-pbe-dn-rrkjus_psl.1.0.0.UPF
 Se2  78.96   Se.rel-pbe-dn-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS (alat)
 Bi     0.3973     0.3973     0.3973  0 0 0
 Bi     0.6027     0.6027     0.6027  0 0 0
 Se1    0.0000     0.0000     0.0000  0 0 0
 Se2    0.2079     0.2079     0.2079  0 0 0
 Se2    0.7821     0.7821     0.7821  0 0 0
K_POINTS (automatic)
  8 8 8 0 0 0

&control
calculation = 'bands'
prefix='bi2se3rel'
restart_mode = 'from_scratch'
wf_collect=.true.,
verbosity='high',
outdir= '/home/name/QEoutput'
pseudo_dir='/home/name/quantum_espresso/q-e-qe-6.5/pseudo'
etot_conv_thr = 1e-5
forc_conv_thr = 1e-4
/
&system
ibrav = -5, celldm(1) = 18.6947, celldm(4) = 0.9135, nat = 5, ntyp = 3,
ecutwfc = 40, ecutrho = 500,
rhombohedral = .true.,
noncolin=.true.,lspinorb=.true.,starting_magnetization=0.,
nbnd=78,
vdw_corr = 'grimme-d2'
/
&electrons
conv_thr = 1.0e-8,
diago_full_acc=.true.,
/
ATOMIC_SPECIES
 Bi   208.98  Bi.rel-pbe-dn-rrkjus_psl.1.0.0.UPF
 Se1  78.96   Se.rel-pbe-dn-rrkjus_psl.1.0.0.UPF
 Se2  78.96   Se.rel-pbe-dn-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS crystal
 Bi     0.3973     0.3973     0.3973  0 0 0
 Bi     0.6027     0.6027     0.6027  0 0 0
 Se1    1.0000     1.0000     1.0000  0 0 0
 Se2    0.2079     0.2079     0.2079  0 0 0
 Se2    0.7821     0.7821     0.7821  0 0 0
K_POINTS crystal_b
5
 0.00000      0.00000      0.00000     20 !gG
 0.50000      0.50000      0.50000     20 !Z
 0.50000      0.50000     -0.00000     20 !F
 0.00000      0.00000      0.00000     20 !gG
 0.00000      0.00000     -0.50000     20  !L1

Thank you,
Varrick Suezaki
Department of Physics and Astronomy
University of California, Riverside
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