Dear Jayraj,
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).
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.
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).
stefano
On 16/03/24 13:56, Lorenzo Paulatto wrote:
On 16/03/2024 12:17, Jayraj Anadani wrote:
hello Paulatto,
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.
Dear Jayraj,
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.
kind regards
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Dr. Lorenzo Paulatto
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
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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 (www.max-centre.eu)
users mailing listus...@lists.quantum-espresso.org
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_______________________________________________
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 (www.max-centre.eu)
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