hi,there!
i have been working to compute the pressure of a group of water molecules in a box but not all the molecules.
i tried compute stress/atom and compute reduce sum but the the pressure got fluctuated intensely .
then i tried compute chunk/atom and want to but now i have no idea about my original plan .
can u provide some method to do that?
thanks inadvance!
hi,there!
i have been working to compute the pressure of a group of water molecules
in a box but not all the molecules.
i tried compute stress/atom and compute reduce sum but the the pressure got
fluctuated intensely .
microscopic pressures *do* fluctuate massively. the more the smaller
the group/volume is.
pressure, like temperature, is a bulk property and we can only compute
it microscopically because we assume equipartitioning, i.e. a system
in equilibrium and then you can average over time as well as over
volume.
this whole "how to compute pressure of subsets of a system" has been
discussed on this mailing list so many times, that most people handing
around here since a long time ago and growing tired of it. please
study those many discussions in the mailing list archives, and
correlate this with what you find in a text book on statistical
thermodynamics and then be enlightened.
axel.