Your initial structure for the SCF calculation does not look right to
me, one of the Se layers is almost interleaved with a Bi layer. The
atomic positions of the bands calculation is also not perfect: the
coordinate of the two Se2 atoms should sum to 1 exactly, while they do
not. This breaks the crystal symmetry and, for such a small gap as
Bi2Se3, is going to have an impact.
I have an input file for Bi2Se3, but I think it will save you a lot of
time in the long run, if you work it out on your own once (It surely
took me some time the first time).
cheers
On 2020-11-17 10:19, Varrick Suezaki wrote:
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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_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
