System equilibrium

Science Talk
1

Hi,

I wanted to equilibrate my bulk system at specific temperature and pressure, and I used NPT ensemble. The temperature is easy to get close to the expected value with small fluctuations, but pressure does not. I checked the archived posts on the forum, someone mentioned that
'The magnitude of pressure fluctuations depends strongly on compressibility, system size, and choice of time step. ’
I’m wondering if there’s an equation to calculate the fluctuation magnitude? So that I can understand what magnitude of fluctuation is valid.

Many thanks.

2

That is not really a LAMMPS question, but a question about statistical thermodynamics.
Thus, I am moving this to the Science Talk category, which is a better fit.
You may also consult textbooks and the published literature.

3

Thanks!