External pressure over system

Hi ; all of you
I have used the Lammps in the simulation.
System Contains:

  1. layer of graphene (500 atom of carbon) as piston (high pressure) and The area of graphene is 1290.5 A2
  2. 2598 molecule of water and 10 pair of NaCl in feed reserve
  3. graphene as membrane
  4. 780 molecule of water in permeate reserve
  5. layer of graphene (500 atom of carbon) as piston (Low pressure) and The area of graphene is 1290.5 A2
  • The first question
    I want to apply 1000 atmosphere of pressure to feed reservoir (and 1 atmosphere of pressure to permeate reservoir separately) and I want to calculate the pressure . Is it enough to consider number of carbon and area of carbon in each piston? Or I should consider the number of water molecules in each reservoir?
    I calculated for 1000 atmosphere (came below) but it did not apply even amount of 1 atmosphere in magnitude in simulation .and I think , I am wrong .
    ?kcal/mol.A=1000atm * 1/500 atom * 1290 A2 (area)* 6.022 e 23 atom /1mol * 1L/1 e27 A3 *0.101325 KJ/1 L.atm * 1Kcal/4.184 KJ = 0. 038 Kcal/mol.A

  • The second question
    I have calculated a pressure and run the simulation. It seems that the pressure is not constant during the simulation . pressure increase in feed reservoir, when number of water molecules decrease and pressure decrease in permeate reservoir ,when number of water molecules increase during simulation (Because of water passes through the pore). How can I apply constant pressure throughout the simulation?
    I think that the number of water molecules in calculation of pressure are important.is it Right?
    Best regards,


two comments (and no answer):

- there is no need to repost the exact same inquiry without having
waited at least two days. people don't always have time to answer
complex questions

- practically everything you ask about are not LAMMPS problems, but
questions about your research and how to do MD simulations for the
kind of system you are interested in. that is something, that you need
to discuss with your adviser or collaborators, as it usually requires
a significant effort to think about what you want to do and how to
develop or adjust a suitable strategy. you cannot expect people on a
mailing list to do what is essentially part of your research work
(i.e. properly design your experiment) for you.