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<div class="moz-cite-prefix">On 1/11/24 20:57, Md. Jahid Hasan Sagor
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAC5Hid83JHzEz7dM7UFjG9V9kYA+d53KyOns+pHzY4fsK6xdDQ@mail.gmail.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<div dir="ltr">Hi Dr. Paulatto,
<div><br>
</div>
<div>Thank you for your advice. I also like your idea about
epsilon.x. But the dielectric function we get using epsilon.x
(QE), Isn't it for only 0 K? How can I extend it to another
temperature?</div>
</div>
</blockquote>
<p>It is computed with an electronic temperature of 0K, but it is
exactly the same as in the paper you are trying to reproduce. But
this is not a big deal, there is very little direct effect of
temperature on electrons: compare the energy of thermal excitation
(k_B T) with the band gap of GaAs and you will see why. I.e.
electron orbitals are far too rigid to be affected by temperature,
especially in insulators. Even in metal we use fictitious
electronic temperature to speed up integration (aka smearing) that
is of the order of 1'000K, and it does not change the electronic
structure much. The effect only come through the motion of ions,
so move the ions and you got finite temperature. </p>
<p>But do not believe me: change the electronic occupation to
"smearing" and set a Fermi-Dirca smearing which is equivalent to
the temperature you want (it is in Ry, i.e. 1 Ry = <span
style="color:#000000;background-color:#ffffff;">157'887 K)</span>.
Then see how, much the total energy and band structure change. how
many k-points do you need to have a discernible Fermi surface at
the to of valence band, etc.<br>
</p>
hth<br>
<p><br>
</p>
<blockquote type="cite"
cite="mid:CAC5Hid83JHzEz7dM7UFjG9V9kYA+d53KyOns+pHzY4fsK6xdDQ@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>Best</div>
<div>Md Jahid</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Jan 11, 2024 at
2:36 PM Lorenzo Paulatto <<a
href="mailto:lorenzo.paulatto@cnrs.fr"
moz-do-not-send="true" class="moz-txt-link-freetext">lorenzo.paulatto@cnrs.fr</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 style="padding-bottom:1px">
<p><br>
</p>
<div>On 11/01/2024 20:06, Md. Jahid Hasan Sagor wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Hi Dr. Paulatto,
<div><br>
</div>
<div>Thank you so much for your suggestions. I was going
in the wrong direction. So if I use your recommended
code (<a
href="https://anharmonic.github.io/thermal2/#d3_r2qx-code"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://anharmonic.github.io/thermal2/#d3_r2qx-code</a>),
would I be able to generate the following figure for
Bulk GaAs?</div>
</div>
</blockquote>
<p>No. The anharmonic code is about vibrational properties.<br>
</p>
<blockquote type="cite">
<div dir="ltr">
<div><br>
</div>
<div>Actually my main goal is to calculate dielectric
function at different temperatures (not 0 K).</div>
</div>
</blockquote>
<p>You can try to do like in the paper. Or you can try a
different approach, i.e. replacing the sampling via
molecular dynamics with a stochastic sampling, like the
one provided by the SSCHA code <a href="http://sscha.eu/"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">http://sscha.eu/</a>,
which is also compatible with QE. Anyway, the supercell
they use is tiny (8 atoms, which is just the simple-cubic
form of GaAs), you should be able to use the epsilon.x
code that comes with QE (check the manual in
PP/Doc/man_eps.pdf). I would say, start with just epsilon
as a function of the volume, test convergence and see if
you can afford it,.<br>
</p>
<p>kind regards</p>
<p><br>
</p>
<blockquote type="cite">
<div dir="ltr">
<div><br>
</div>
<div>Thanks</div>
<div>Md Jahid Hasan</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Jan 11, 2024
at 9:19 AM Lorenzo Paulatto <<a
href="mailto:lorenzo.paulatto@cnrs.fr"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">lorenzo.paulatto@cnrs.fr</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 style="padding-bottom:1px">
<p>Hello Jahid,</p>
<p>I have read the article very quickly, but I do
not think they use the RMS to compute epsilon. All
they do is compute epsilon for a few sample atomic
potisions reached during the MD run, then they
average it. The "Theoretical Method" section does
not have any logic, but it is explained in the
"Conclusions". The RMS seems to be only used to
ascertain the validity of the simulation.<br>
</p>
<div>hth</div>
<div><br>
</div>
<div>On 1/11/24 04:42, Md. Jahid Hasan Sagor wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>Hi Dr. Paulatto,</div>
<div><br>
</div>
<div>Thank you so much for your comments.</div>
<div><br>
</div>
<div>Actually, The paper (attached) extracted
the temperature of each configuration from the
mean square displacement per atom of the
configuration (GaAs). In the harmonic
approximation, they determined the
relationship between mean square displacement
and temperature T from the phonon density of
states of bulk GaAs calculated by Giannozzi et
al. The equation as follows: </div>
<div><br>
</div>
<div><img
src="cid:part1.I67q7zjY.tjHE0ngq@cnrs.fr"
alt="image.png" class="" width="371"
height="117"></div>
<div>Here is the figure they generated <br>
</div>
<div><img
src="cid:part2.UtrxujYh.h0gdBliJ@cnrs.fr"
alt="image.png" class="" width="540"
height="428"><br>
</div>
<div><br>
</div>
<div>So, now If I can find out the RMS of GaAs
using CPMD, I will try to observe the
corresponding configuration of GaAs atoms.
Finally, the atomic positions will be the
input of Quantum Espresso pw.x etc ( I mean
normally how do we calculate dielectric
constant in QE).</div>
<div><br>
</div>
<div>Can I use it ( <a
href="https://anharmonic.github.io/thermal2/#d3_r2qx-code"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://anharmonic.github.io/thermal2/#d3_r2qx-code</a>)
for the same purpose? </div>
<div><br>
</div>
<div>Best</div>
<div>Hasan<br>
</div>
<div> </div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Jan
10, 2024 at 3:13 PM Lorenzo Paulatto <<a
href="mailto:lorenzo.paulatto@cnrs.fr"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">lorenzo.paulatto@cnrs.fr</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 style="padding-bottom:1px">
<p>I would guess that you calculate the
static dielectric constant at the
temperature-dependent volume
(experimental, or quasi-harmonic) and you
are 90% of the way there. Do you have a
specific reason to believe that it would
be proportional to the RMS ?</p>
<p>Btw, the code d3_r2q.x included with the
"anharmonic" package can compute the RMS
from an inexpensive phonon calculation,
maybe have a look at it before doing a
large supercell MD.</p>
<p><a
href="https://anharmonic.github.io/thermal2/#d3_r2qx-code"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://anharmonic.github.io/thermal2/#d3_r2qx-code</a><br>
</p>
<div>cheers<br>
</div>
<div><br>
</div>
<div>On 10/01/2024 19:35, Md. Jahid Hasan
Sagor wrote:<br>
</div>
<blockquote type="cite">
<div dir="auto">
<div>Actually, I have to calculate
Dielectric constant for GaAs for
different temperatures (not 0 k). To
do that, I need to extract atomic
positions for different RMS using
CPMD. If anyone know someone/ or give
some guidelines, it would be great
help for me.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Thank you.<br>
<br>
<div class="gmail_quote" dir="auto">
<div dir="ltr" class="gmail_attr">On
Tue, Jan 9, 2024, 2:09 PM Md.
Jahid Hasan Sagor <<a
href="mailto:md.sagor@maine.edu"
target="_blank"
moz-do-not-send="true"
class="moz-txt-link-freetext">md.sagor@maine.edu</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 dir="ltr">Dear QE community,
<div><br>
</div>
<div>I want to calculate the
mean square displacement of
GaAs using CPMD. From the mean
square displacement, I want to
extract the configuration of
atoms (e.g atomic position of
Ga and As). Could anyone
please give me some guidelines
on how I can perform it?
Should I use only the cp.x
package or by other means?
Your time and suggestions
would be a great help for me.</div>
<div><br>
</div>
<div>Best Regards</div>
<div>Md Jahid Hasan</div>
<div>PhD Student, Mechanical
Engineering</div>
<div>University of Maine</div>
</div>
</blockquote>
</div>
</div>
</div>
<br>
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<pre>_______________________________________________
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</blockquote>
<div>-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 &
Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype:
paulatz<br>
<a
href="http://www.impmc.upmc.fr/~paulatto/" target="_blank"
moz-do-not-send="true"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a
href="https://anharmonic.github.io/"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252
Paris CX 05</small></div>
</div>
_______________________________________________<br>
The Quantum ESPRESSO community stands by the
Ukrainian<br>
people and expresses its concerns about the
devastating<br>
effects that the Russian military offensive
has on their<br>
country and on the free and peaceful
scientific, cultural,<br>
and economic cooperation amongst peoples<br>
_______________________________________________<br>
Quantum ESPRESSO is supported by MaX (<a
href="http://www.max-centre.eu"
rel="noreferrer" target="_blank"
moz-do-not-send="true">www.max-centre.eu</a>)<br>
users mailing list <a
href="mailto:users@lists.quantum-espresso.org" target="_blank"
moz-do-not-send="true"
class="moz-txt-link-freetext">users@lists.quantum-espresso.org</a><br>
<a
href="https://lists.quantum-espresso.org/mailman/listinfo/users"
rel="noreferrer" target="_blank"
moz-do-not-send="true"
class="moz-txt-link-freetext">https://lists.quantum-espresso.org/mailman/listinfo/users</a></blockquote>
</div>
</blockquote>
<div>-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne
Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX
05</small></div>
</div>
</blockquote>
</div>
</blockquote>
<div>-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05</small></div>
</div>
</blockquote>
</div>
</blockquote>
<div class="moz-signature">-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/"
class="moz-txt-link-freetext">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05<small></small></small></div>
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