Hi all-
I was wondering if there is a way using the current algorithms within lammps (and maybe using some clever LAMMPS script language) to remove molecules as they pass out of one side of the box and add them back into the other side of the box with a randomly distributed velocity?
Cheers-
Chris
Hi Chris. There’s no such algorithm already in LAMMPS. There are some features with similar aspects that you could potentially borrow from:
http://lammps.sandia.gov/doc/fix_thermal_conductivity.html
http://lammps.sandia.gov/doc/fix_viscosity.html
Might be possible to write up a clever script to do what you want. Note that there are create_atoms, delete_atoms, set, and velocity commands that have aspects of what you’re looking for. But I think it would be better to write up your own fix to do what you want, that leverages existing code by calling relevant existing functions.
Paul
Hi all-
hi chris,
I was wondering if there is a way using the current algorithms within lammps
(and maybe using some clever LAMMPS script language) to remove molecules as
they pass out of one side of the box and add them back into the other side
of the box with a randomly distributed velocity?
i don't think this can be done without writing new code.
and if you look at molecules, LAMMPS currently more-or-less
requires that the total number remains constant. there are some
provisions to create individual atoms and creating/breaking
bonds, but nothing for angles, dihedrals etc.
with periodic boundary conditions, you essentially have
the feature of having molecules passing through one
face of the box and re-appearing on the other. what
you could implement would be some kind of "slipstream zone"
that would take atoms/molecules entering a predefined
region and adding/redistributing forces/velocities to them,
so the accelerate away from one side of the face to
the other before they get pushed back into the system.
you would probably have to combine this with a second,
"gooey zone" where the particles get slowed down again
and can re-enter the "normal" area without adding an
overall momentum to the system (unless that is desired).
cheers,
axel.