NPT monte carlo simulation pressure calculation

[pyscho]

Hello all,

I have been working on an NPT monte carlo simulation. I would like to know how I can measure the instantaneous pressure of the system at each monte carlo step?

 

[UltrafastPED]

Like this: https://en.wikipedia.org/wiki/Molecular_dynamics#Isothermal.E2.80.93isobaric_.28NPT.29_ensemble

It says that the pressure is conserved.

I would think that you just "measure" the momentum hitting the walls ...

 

[pyscho]

I am applying periodic boundary conditions, and my atoms are sitting on their lattice sites (pretty much). I am trying to figure out the optimum lattice constant for a given pressure and temperature. However, I would like to "monitor" the pressure of the system as a function of monte carlo steps. In NVT monte carlo simulations, even the system reaches a thermal equilibrium with the heat bath, there is still fluctuations in temperature in the system (not the heat bath) besides energy fluctuations. Similar thing is also true for NPT, but I don't exactly know how to measure those fluctuations in NPT monte carlo simulation. I am digging something that has to do with virial, but not sure how to use it at the moment.

 

[Useful nucleus]

pyscho, NPT monte Carlo is standard now since it was introduced by S. Yip and coworkers in late 80's. Consult the text "Understanding Molecular Simulation" by Daan Frenkel for more information and references to the original papers.

Here is an amazon link for the book:
https://www.amazon.com/dp/0122673514/?tag=pfamazon01-20