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<p>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.</p>
<p>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).</p>
<p>cheers<br>
</p>
<div class="moz-cite-prefix">On 2020-11-17 10:19, Varrick Suezaki
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CALRHNFYOqr=N1JmPTh7zWSTpXXCdWB7x3w3AaHBEvPLhT29GNw@mail.gmail.com">
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<div dir="ltr">Dear PW users,
<div>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).</div>
<div><br>
</div>
<div>&control<br>
calculation = 'vc-relax'<br>
prefix='bi2se3rel'<br>
restart_mode = 'from_scratch'<br>
outdir= '/home/name/QEoutput'<br>
pseudo_dir='/home/name/quantum_espresso/q-e-qe-6.5/pseudo'<br>
etot_conv_thr = 1e-7<br>
forc_conv_thr = 1e-6<br>
/<br>
&system<br>
ibrav = -5, celldm(1) = 18.6947, celldm(4) = 0.9135, nat = 5,
ntyp = 3,<br>
ecutwfc = 40, ecutrho = 500,<br>
rhombohedral = .true.,<br>
noncolin=.true.,lspinorb=.true.,starting_magnetization=0.,<br>
nbnd=78,<br>
vdw_corr = 'grimme-d2'<br>
/<br>
&electrons<br>
conv_thr = 1.0e-9,<br>
/<br>
&ions<br>
/<br>
&cell<br>
cell_dofree='ibrav'<br>
/<br>
ATOMIC_SPECIES<br>
Bi 208.98 Bi.rel-pbe-dn-rrkjus_psl.1.0.0.UPF<br>
Se1 78.96 Se.rel-pbe-dn-rrkjus_psl.1.0.0.UPF<br>
Se2 78.96 Se.rel-pbe-dn-rrkjus_psl.1.0.0.UPF<br>
<br>
ATOMIC_POSITIONS (alat)<br>
Bi 0.3973 0.3973 0.3973 0 0 0<br>
Bi 0.6027 0.6027 0.6027 0 0 0<br>
Se1 0.0000 0.0000 0.0000 0 0 0<br>
Se2 0.2079 0.2079 0.2079 0 0 0<br>
Se2 0.7821 0.7821 0.7821 0 0 0<br>
K_POINTS (automatic)<br>
8 8 8 0 0 0<br>
</div>
<div><br>
</div>
<div>&control<br>
calculation = 'bands'<br>
prefix='bi2se3rel'<br>
restart_mode = 'from_scratch'<br>
wf_collect=.true.,<br>
verbosity='high',<br>
outdir= '/home/name/QEoutput'<br>
pseudo_dir='/home/name/quantum_espresso/q-e-qe-6.5/pseudo'<br>
etot_conv_thr = 1e-5<br>
forc_conv_thr = 1e-4<br>
/<br>
&system<br>
ibrav = -5, celldm(1) = 18.6947, celldm(4) = 0.9135, nat = 5,
ntyp = 3,<br>
ecutwfc = 40, ecutrho = 500,<br>
rhombohedral = .true.,<br>
noncolin=.true.,lspinorb=.true.,starting_magnetization=0.,<br>
nbnd=78,<br>
vdw_corr = 'grimme-d2'<br>
/<br>
&electrons<br>
conv_thr = 1.0e-8,<br>
diago_full_acc=.true.,<br>
/<br>
ATOMIC_SPECIES<br>
Bi 208.98 Bi.rel-pbe-dn-rrkjus_psl.1.0.0.UPF<br>
Se1 78.96 Se.rel-pbe-dn-rrkjus_psl.1.0.0.UPF<br>
Se2 78.96 Se.rel-pbe-dn-rrkjus_psl.1.0.0.UPF<br>
<br>
ATOMIC_POSITIONS crystal<br>
Bi 0.3973 0.3973 0.3973 0 0 0<br>
Bi 0.6027 0.6027 0.6027 0 0 0<br>
Se1 1.0000 1.0000 1.0000 0 0 0<br>
Se2 0.2079 0.2079 0.2079 0 0 0<br>
Se2 0.7821 0.7821 0.7821 0 0 0<br>
K_POINTS crystal_b<br>
5<br>
0.00000 0.00000 0.00000 20 !gG<br>
0.50000 0.50000 0.50000 20 !Z<br>
0.50000 0.50000 -0.00000 20 !F<br>
0.00000 0.00000 0.00000 20 !gG<br>
0.00000 0.00000 -0.50000 20 !L1<br>
</div>
<div><br>
</div>
<div>Thank you,</div>
<div>Varrick Suezaki</div>
<div>Department of Physics and Astronomy</div>
<div>University of California, Riverside</div>
</div>
<br>
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