I would like to know how to apply a pressure difference to a group of atoms?
Suppose I have a water slab which is periodic in x and y dimension, now I’d
like to apply, say, 2 atm pressure to the slab along z axis in the positive direction,
while apply, 1 atm pressure to the slab along z axis in the negative direction.
I’m now using addforce to the atom to mimic a net pressure difference,
but forces applied to each atoms are the same which seemed not consistent with
what should be in the real case.
Any suggestion is highly appreciated~