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<p>Dear Jayraj,</p>
<p>adding to what Lorenzo already replied, P and V as well as E and
T are conjugated quantities: if you fix one the other fluctuates
(of an amount \propto 1/sqrt N that vanishes in the thermodynamic
limit).</p>
<p>so you can have NVE simulations where the average kinetic energy
is related to the system temperature but fluctuates in time, or
using a thermostat you can fix the system temperature (sampling
NVT ensemble) but you give up energy conservation.</p>
<p>the same for V and P, you can have NVT and NPT, or NVE and NPH
(because the conserved quantity is in this case the enthalpy). The
larger the system the smaller the fluctuations but for finite
number of particles the fluctuations are always present (and the
thermostats and barostats do have their own degrees of freedom
whose contribution become negligible in the thermodynamic limit).<br>
</p>
<p>stefano<br>
</p>
<div class="moz-cite-prefix">On 16/03/24 13:56, Lorenzo Paulatto
wrote:<br>
</div>
<blockquote type="cite" cite="mid:52918096-ca11-4cf5-b53e-e5623adc9cef@cnrs.fr">
<div class="moz-cite-prefix">On 16/03/2024 12:17, Jayraj Anadani
wrote:<br>
</div>
<blockquote type="cite" cite="mid:CAFZg28uyoYtXK6Asst+BmieAYzjOa3_RtPoGfRaNK15DTJ7R=Q@mail.gmail.com">
<div dir="ltr">hello <span style="color:rgb(31,31,31);font-size:0.875rem;font-family:"Google
Sans",Roboto,RobotoDraft,Helvetica,Arial,sans-serif">Paulatto</span>,
<div>but in cell_dynamics all options for pressure control are
for vc-md and vc-relax. and i want to control pressure
during ion_temperature=reduce-T option.</div>
</div>
</blockquote>
<p>Dear Jayraj,</p>
<p>it is not very clear what you want to do. You can have constant
NVT, or NVE or NPT, or NPE. But it looks to me that you want
constant instantaneous P and V, which is impossible as P is a
macroscopic quantity, it only makes sense on average.<br>
</p>
<p>kind regards<br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:CAFZg28uyoYtXK6Asst+BmieAYzjOa3_RtPoGfRaNK15DTJ7R=Q@mail.gmail.com">
<br>
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<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" moz-do-not-send="true">http://www.impmc.upmc.fr/~paulatto/</a>
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<pre class="moz-quote-pre" wrap="">_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu">www.max-centre.eu</a>)
users mailing list <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
<a class="moz-txt-link-freetext" href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a></pre>
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