Macro-nano coupling. Pressure inlet condition in LAMMPS

Dear all,

in my research about how a polymer gets into a nanocavity I am facing the following problem:

From a macro scale simulation carried out using Solidworks Plastics, I have a pressure profile (P with time). I want to use this pressure profile as a boundary condition in my LAMMPS simulation box but, as far as I know, it is not possible to define a pressure inlet boundary condition in molecular dynamics. So, how could I couple my pressure profile extracted from Solidworks with LAMMPS?

Maybe I should set a moving wall? However, at which speed?

Or maybe I should use the aveforce command at all the atoms of the simulation box? Should the force, then, be Pressure*Surface_of_inlet_wall?

Thanks in advance,

Jordi Pina

Dear all,

in my research about how a polymer gets into a nanocavity I am facing the
following problem:

From a macro scale simulation carried out using Solidworks Plastics, I have
a pressure profile (P with time). I want to use this pressure profile as a
boundary condition in my LAMMPS simulation box but, as far as I know, it is
not possible to define a pressure inlet boundary condition in molecular
dynamics. So, how could I couple my pressure profile extracted from
Solidworks with LAMMPS?

Maybe I should set a moving wall? However, at which speed?

Or maybe I should use the aveforce command at all the atoms of the
simulation box? Should the force, then, be Pressure*Surface_of_inlet_wall?

that sounds much more reasonable and doable.
in the end, it is up to you.

you have to keep in mind, though, that there is no simple 1:1
translation from macroscopic models to atomic scale models.

axel.

There is a also a recently added fix controller command

which could be used to equilibrate the position of a wall

to induce a target pressure.

Steve