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<p>As you Laurence, I was thinking about the effect of shifting or
not the kmesh! <br>
</p>
<p>Peter, do you think it will lead to a better convergence? <br>
</p>
<p>Cheers</p>
<p>Xavier<br>
</p>
<br>
<div class="moz-cite-prefix">Le 03/09/2018 à 13:59, Laurence Marks a
écrit :<br>
</div>
<blockquote
cite="mid:CANkSMZBLR74ZTfhXuG-srbvsWwAOLgAVn3XKnbtvaAEqSgDYjw@mail.gmail.com"
type="cite">
<div dir="ltr">What you are doing "should" work -- I have done
similar things myself. I have also managed to do it "not quite
right" in the past as well. The most obvious possibility is user
error.
<div><br>
</div>
<div>One thing I would check is shifting the k-mesh. For reasons
that I do not fully understand this can break symmetry. A good
thing to check is no shift, this may solve the problem. You
may want to test using TEMPS.</div>
<div><br>
</div>
<div>You may also need to tighten the convergence. Breaking of
symmetry can be a very soft mode, and be only satisfied when
one pushes to really well converged results.</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Sun, Sep 2, 2018 at 10:33 PM, Oleg
Rubel <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:rubelo@mcmaster.ca" target="_blank">rubelo@mcmaster.ca</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Dear
Wien2k community,<br>
<br>
I try to compute opto-elastic properties of InP (zinc-blend
structure). <br>
It is related to a change of the dielectric constant (real
part) in <br>
response to an applied strain. There are no problems with a
response to <br>
a hydrostatic strain, and results agree well with
experiments. A problem <br>
occurs with a uniaxial strain (strained along X-axis only by
0.05%). <br>
Computed change in the dielectric constant is too large (~
an order of <br>
magnitude).<br>
<br>
Trying to trace back the problem, I did the following:<br>
First, I initialize a tetragonaly-distorted zinc-blend
structure <br>
(init_lapw -b -vxc 19 -ecut -6.5 -numk 800) with the
following lattice <br>
parameters<br>
<br>
F LATTICE,NONEQUIV.ATOMS: 2 <br>
<br>
MODE OF CALC=RELA unit=ang <br>
<br>
11.095785 11.090240 11.090240 90.000000 90.000000
90.000000<br>
<br>
Then I set the lattice parameters back to the cubic lattice<br>
<br>
F LATTICE,NONEQUIV.ATOMS: 2 <br>
<br>
MODE OF CALC=RELA unit=ang <br>
<br>
11.090240 11.090240 11.090240 90.000000 90.000000
90.000000<br>
<br>
and rerun (x dstart). This allows me to preserve the
symmetry of a <br>
distorted structure (see the structure file below).<br>
<br>
Next, I run SCF (run_lapw -ec 0.00001 -cc 0.0001) and optics
with <br>
20x20x20 k-mesh. The results for Re and Im parts of the
dielectric <br>
constant are here:<br>
<br>
[oleg@feynman InP-w2k]$ head InP-w2k.epsilon<br>
# <br>
<br>
# Lorentzian broadening with gamma= 0.100000 [eV]<br>
# Im(epsilon) shifted by 0.7860 [eV]<br>
# No intraband contributions added<br>
#<br>
# Energy [eV] Re_eps_xx Im_eps_xx Re_eps_yy
Im_eps_yy<br>
#<br>
0.013610 0.940850E+01 0.988634E-01 0.947674E+01
0.100908E+00<br>
0.040820 0.940928E+01 0.100340E+00 0.947756E+01
0.102453E+00<br>
0.068030 0.941084E+01 0.101855E+00 0.947919E+01
0.104042E+00<br>
<br>
It seems that the symmetry is broken, which causes later
problems with <br>
opto-elastic coefficients as change of 0.07 in the second
decimal point <br>
of Re_eps for such a small strain is too much.<br>
<br>
Once again, there are no problems when the strain tensor
does not break <br>
the zinc-blend cubic symmetry.<br>
<br>
Any thoughts are highly appreciated.<br>
<br>
<br>
Thank you in advance<br>
Oleg<br>
<br>
-- <br>
Oleg Rubel (PhD, PEng)<br>
Department of Materials Science and Engineering<br>
McMaster University<br>
JHE 359, 1280 Main Street West, Hamilton, Ontario L8S 4L8,
Canada<br>
Email: <a moz-do-not-send="true"
href="mailto:rubelo@mcmaster.ca">rubelo@mcmaster.ca</a><br>
Tel: +1-905-525-9140, ext. 24094<br>
Web: <a moz-do-not-send="true"
href="https://urldefense.proofpoint.com/v2/url?u=http-3A__olegrubel.mcmaster.ca&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=WpMS0L_jtI19kiPXo_QJrB9iBMQX1L9TeNePUM_x2Lw&s=YKfgMS8xLL_yM_B62Rds1s_GApfimaNcCR8kQSU2LLw&e="
rel="noreferrer" target="_blank">https://urldefense.proofpoint.<wbr>com/v2/url?u=http-3A__<wbr>olegrubel.mcmaster.ca&d=<wbr>DwICAg&c=<wbr>yHlS04HhBraes5BQ9ueu5zKhE7rtNX<wbr>t_d012z2PA6ws&r=U_<wbr>T4PL6jwANfAy4rnxTj8IUxm818jnvq<wbr>KFdqWLwmqg0&m=WpMS0L_<wbr>jtI19kiPXo_<wbr>QJrB9iBMQX1L9TeNePUM_x2Lw&s=<wbr>YKfgMS8xLL_yM_B62Rds1s_<wbr>GApfimaNcCR8kQSU2LLw&e=</a><br>
<br>
P.S. I run WIEN2k_16.1 (Release 11/17/2016). Our main
cluster is down <br>
for maintenance, so I was not able to check with the newest
version of <br>
Wien2k.<br>
<br>
P.P.S. Here is the cubic structure file with a distorted
symmetry that I <br>
run to get the data.<br>
<br>
InP <br>
<br>
F LATTICE,NONEQUIV.ATOMS: 2 <br>
<br>
MODE OF CALC=RELA unit=ang <br>
<br>
11.090240 11.090240 11.090240 90.000000 90.000000
90.000000 <br>
<br>
ATOM -1: X=0.00000000 Y=0.00000000 Z=0.00000000<br>
MULT= 1 ISPLIT=-2<br>
In NPT= 781 R0=0.00001000 RMT= 2.0000 Z:
49.000 <br>
<br>
LOCAL ROT MATRIX: 0.0000000 0.0000000 1.0000000<br>
1.0000000 0.0000000 0.0000000<br>
0.0000000 1.0000000 0.0000000<br>
ATOM -2: X=0.25000000 Y=0.25000000 Z=0.25000000<br>
MULT= 1 ISPLIT=-2<br>
P NPT= 781 R0=0.00010000 RMT= 2.0000 Z:
15.000 <br>
<br>
LOCAL ROT MATRIX: 0.0000000 0.0000000 1.0000000<br>
1.0000000 0.0000000 0.0000000<br>
0.0000000 1.0000000 0.0000000<br>
8 NUMBER OF SYMMETRY OPERATIONS<br>
1 0 0 0.00000000<br>
0-1 0 0.00000000<br>
0 0-1 0.00000000<br>
1<br>
1 0 0 0.00000000<br>
0 0-1 0.00000000<br>
0-1 0 0.00000000<br>
2<br>
-1 0 0 0.00000000<br>
0 1 0 0.00000000<br>
0 0-1 0.00000000<br>
3<br>
-1 0 0 0.00000000<br>
0 0 1 0.00000000<br>
0-1 0 0.00000000<br>
4<br>
-1 0 0 0.00000000<br>
0 0-1 0.00000000<br>
0 1 0 0.00000000<br>
5<br>
-1 0 0 0.00000000<br>
0-1 0 0.00000000<br>
0 0 1 0.00000000<br>
6<br>
1 0 0 0.00000000<br>
0 0 1 0.00000000<br>
0 1 0 0.00000000<br>
7<br>
1 0 0 0.00000000<br>
0 1 0 0.00000000<br>
0 0 1 0.00000000<br>
8<br>
______________________________<wbr>_________________<br>
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<br>
<br clear="all">
<div><br>
</div>
-- <br>
<div class="gmail_signature" data-smartmail="gmail_signature">
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr"><span style="font-size:12.8px">Professor
Laurence Marks</span><br>
</div>
<div dir="ltr"><span style="font-size:12.8px">"Research
is to see what everybody else has seen,
and to think what nobody else has
thought", </span><span
style="font-size:12.8px">Albert
Szent-Gyorgi</span><br>
<a moz-do-not-send="true"
href="http://www.numis.northwestern.edu"
target="_blank">www.numis.northwestern.edu</a> ; <span
style="font-size:12.8px">Corrosion in 4D:
</span><a moz-do-not-send="true"
href="http://MURI4D.numis.northwestern.edu"
style="font-size:12.8px" target="_blank">MURI4D.numis.northwestern.edu</a>
<div><span style="font-size:12.8px">Partner
of the CFW 100% program for gender
equity, </span><a moz-do-not-send="true"
href="http://www.cfw.org/100-percent"
style="font-size:12.8px" target="_blank">www.cfw.org/100-percent</a></div>
<div>Co-Editor, Acta Cryst A</div>
</div>
</div>
</div>
</div>
</div>
</div>
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