[lammps-users] Apply an external pressure

How are you modeling the piston - as a wall via a fix wall command,
or as a group of frozen atoms? In the former case you can move
the wall over time and monitor the force on it. In the latter you
can use fix aveforce and also monitor the force on the atoms
of the wall.


Hello, Steve,

   Many thanks for your suggestions. The piston is modeled by group of frozen atoms.
If there is no velocity applied on the piston, and only an external pressure is applied to the piston,
can the command fix aveforce model the constant pressure?

Have a good day


Well it can apply an average force, balanced by the fluid
pushing back. If you divided force by area you have pressure.