<div dir="ltr">Thank you all for your response. For computing the Z* and epilson for polar materials, I saw in a couple of tutorials that I have to first compute the dynamic matrix using dynmat.x at the Gamma point setting epsil=.true.. For the remaining q-points, I have to add the non-analytical part in the input of the dynmat.x. Is this the correct for version 6.4.1 or should I just have to set some flags? <div><br></div><div> Also, is there a difference if I use matdyn.x instead of dynmat.x? </div><div><br></div><div>Regards,</div><div>Sheikh</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Dec 30, 2019 at 5:34 PM Stefano de Gironcoli <<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
<p><tt>the order of the entries in the pseudopotential list or in
the atomic position list should not affect the result.</tt></p>
<p><tt>however you are not changing only the order. <br>
</tt></p>
<p><tt>1) you are also swapping the two atoms... this too should not
change anything but is not the same as changing the order only
:)<br>
</tt></p>
<p><tt>2) the first calculation is metallic (with a quite large
gaussian smearing, 0.05 Ry is ~ 0.7 eV) the second uses the
default insulating setting. THIS may have a big impact, for two
reasons: i) the fundamental gap in AlSb, if I remember
correctly, is not very large .. comparable to the smearing width
used; ii) being AlSb a polar material the vibrational properties
have a non analytic component ruled by the macroscopic
dielectric properties (Z*, epsilon_infty) that are disabled in
the phonon calculation of metals (where epsilon_infty diverges).
<br>
</tt></p>
<p><tt>Additionally, in the phonon calculation step you should make
sure you do compute Z* and epsilon and include them in the
subsequent phonon dispersion calculation step. <br>
</tt></p>
<p><tt>HTH</tt></p>
<p><tt>stefano</tt><br>
</p>
<div>On 30/12/19 23:07, Sheikh Ziauddin
Ahmed wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">I am trying to calculate the phonon dispersion of
AlSb. I am getting two different results depending on how I am
introducing the atoms in the SCF calculation. Will the order of
the atom change the symmetry of the zinc blende AlSb?
<div><br>
</div>
<div>In the first case the input deck is: </div>
<div>&system<br>
ibrav=2, nat=2, ntyp=2,<br>
ecutwfc = 50, ecutrho = 500,<br>
occupations='smearing',<br>
smearing='gauss',<br>
degauss=0.05,<br>
celldm(1)=11.5944146,<br>
/<br>
&electrons<br>
conv_thr = 1.0e-12<br>
mixing_beta = 0.7<br>
mixing_mode = 'local-TF'<br>
/<br>
ATOMIC_SPECIES<br>
Al 26.98 al_lda_v1.uspp.F.UPF<br>
Sb 121.76 sb_lda_v1.4.uspp.F.UPF<br>
ATOMIC_POSITIONS (alat)<br>
Al 0.0 0.0 0.0<br>
Sb 0.25 0.25 0.25<br>
K_POINTS automatic<br>
6 6 6 0 0 0<br>
</div>
<div><br clear="all">
<div>In the second case the input deck is: </div>
<div> &system<br>
ibrav=2, nat=2, ntyp=2,<br>
ecutwfc = 50, ecutrho = 500,<br>
!occupations='smearing',<br>
!smearing='gauss',<br>
!degauss=0.05,<br>
celldm(1)=11.5944146,<br>
/<br>
&electrons<br>
conv_thr = 1.0e-12<br>
mixing_beta = 0.7<br>
mixing_mode = 'local-TF'<br>
/<br>
ATOMIC_SPECIES<br>
Sb 121.76 sb_lda_v1.4.uspp.F.UPF<br>
Al 26.98 al_lda_v1.uspp.F.UPF<br>
ATOMIC_POSITIONS (alat)<br>
Sb 0.0 0.0 0.0<br>
Al 0.25 0.25 0.25<br>
K_POINTS automatic<br>
6 6 6 0 0 0<br>
</div>
<div><br>
</div>
<div>Thanks in advance!</div>
-- <br>
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<div style="font-size:12.8px"><font color="#444444"><b>Sheikh Ziauddin
Ahmed </b></font></div>
<div style="font-size:12.8px"><font color="#444444">PhD Candidate</font></div>
<div style="font-size:12.8px"><font color="#444444">Charles L. Brown
Department of Electrical and
Computer Engineering</font></div>
<div style="font-size:12.8px"><font color="#444444">University of
Virginia</font></div>
<div style="font-size:12.8px"><font color="#444444">Email<font color="#888888">:</font><a href="mailto:sza9wz@virginia.edu" target="_blank">sza9wz<u>@virginia.edu</u></a></font></div>
<div>
<div style="font-size:12.8px"><font color="#444444">LinkedIn</font><font color="#000000">: </font><span style="color:rgb(136,136,136);font-size:12.8px"><a href="https://www.linkedin.com/in/sheikh-ziauddin-ahmed" target="_blank">https://www.linkedin.com/in/sheikh-ziauddin-ahmed</a></span></div>
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