<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><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">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"><u></u>
<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">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">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">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:ii_18cfa14df24cb971f161" alt="image.png" width="371" height="117"></div>
<div>Here is the figure they generated <br>
</div>
<div><img src="cid:ii_18cfa14df25cb971f162" alt="image.png" 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">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">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">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">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>
<fieldset></fieldset>
<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">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/" target="_blank">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">www.max-centre.eu</a>)<br>
users mailing list <a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a><br>
<a href="https://lists.quantum-espresso.org/mailman/listinfo/users" rel="noreferrer" target="_blank">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">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/" target="_blank">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">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/" target="_blank">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05<small></small></small></div>
</div>
<u></u><u></u>
</blockquote></div>