In my system all sides are non periodic. Can any one suggest how to control pressure?
Navin
Hi Navin,
For a system with free (non-periodic) sides, you're only hope to prescribe
pressure would be to designate separate groups of atoms for each face of
your system and then create an "addforce" fix where the amount of force per
atom for each face would be estimated using the area of each face, the
number of atoms for each face, and the desired pressure.
Even then, I think that this method may introduce some instabilities in your
simulation. But I'm pretty sure any of the constant pressure fixes require
periodic boundary conditions.
Jon Z.
In my system all sides are non periodic. Can any one suggest how to control
pressure?
navin,
a system without boundaries, is a system in vacuum.
there is no pressure to control and you have to use
the nvt ensemble to begin with.
now if you have a confinement (via a wall potential or fixed
particles) you can have a pressure in _part_ of your system,
by monitoring and controlling the force exerted by that confinement.
if you want that to be automatic, i guess you'd have to programm
your tool (e.g. a "fix" in LAMMPS-speak) that controls the confinement
according to some rules and observables.
cheers,
axel.