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<p>Hello Sergio,</p>
<p>the time constant of the thermostat is a parameter of your
calculation named fnosep in the namelist IONS
(<a class="moz-txt-link-freetext" href="https://www.quantum-espresso.org/Doc/INPUT_CP.html#idm306">https://www.quantum-espresso.org/Doc/INPUT_CP.html#idm306</a>).<br>
Therefore, it's either what you set it to or the default (1THz),
and printed in the output as: nose` frequency(es) =
....<br>
</p>
<p>"how could I infer if thermostat is interacting strong or weakly
according to the magnitude of the time constant":<br>
So, the parameter fnosep is a frequency. To infer how strongly a
thermostat of that frequency couples with your system, you need to
calculate the vibrational density of states (VDOS, also called
power spectrum) of your system, which is the fourier transform of
the velocity-velocity autocorrelation function ideally from an MD
trajectory without a thermostat (NVE).<br>
</p>
<p>The thermostat, generally speaking, will interact strongly with
modes of the same frequency as the thermostat (said fnosep) and
weakly with modes of different frequencies. (see 6.1 of Frenkel
& Smit: Understanding Molecular Simulation: From Algorithms to
Applications).<br>
<span class="pl-en"></span></p>
<p><span class="pl-en">Best,</span></p>
<p><span class="pl-en"> Leonid</span></p>
<p><span class="pl-en">PS: </span><span class="pl-en">To calculate
the power spectrum, there is a Python package to do it, and you
can check the code here: <span class="pl-en"><a class="moz-txt-link-freetext" href="https://github.com/lekah/samos/blob/master/samos/analysis/dynamics.py">https://github.com/lekah/samos/blob/master/samos/analysis/dynamics.py</a>,
function get_power_spectrum</span></span></p>
<p><span class="pl-en"><span class="pl-en"><br>
</span></span></p>
<div class="moz-cite-prefix">On 1/27/20 5:25 AM, Sergio Castaneda
Ramirez wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CACj9RV+ZktYeqE=JKQxZSdYX02oo5HWDdTf+Ju2dXEdddhSbJQ@mail.gmail.com">
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<p class="gmail-x_MsoNormal">Dear experts,</p>
<p class="gmail-x_MsoNormal">I am carrying out a NVT simulation
for a hydrated anion-exchange membrane segment using cp.x. I
am using Nose-Hoover chains as thermostat and I need to show
if the thermostat is interacting strong or weakly with the
system via the time constant of the thermostat. </p>
<p class="gmail-x_MsoNormal">Therefore, I cordially want to ask
you if the time constant of the thermostat is directly
reported in one of the output files of cp.x or, if not
reported, how could I estimate it from output information?
Also, I want to ask you, how could I infer if thermostat is
interacting strong or weakly according to the magnitude of the
time constant?</p>
<p class="gmail-x_MsoNormal">Thanks a lot in advance,</p>
<p class="gmail-x_MsoNormal">Sergio<br>
</p>
</div>
<br>
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