Any Injection and Free Outlet boundary conditions

Dear LAMMPS users,

Suppose we have one channel: the left end is for injection with time-dependent injection rate, and the right end is free outlet. Can anyone direct me to the right place in the Manual for such implementation?

Thanks in advance!

About injection: I just found that “fix deposit” might do such job, but I do not clearly understand its description “Insert a single atom or molecule into the simulation domain every M timesteps until N atoms or molecules have been inserted.” It sounds not like the bulk injection, but only injection of one single atom each time.

Please correct me if it does not make sense.

About injection: I just found that "fix deposit" might do such job, but I do
not clearly understand its description "Insert a single atom or molecule
into the simulation domain every M timesteps until N atoms or molecules have
been inserted." It sounds not like the bulk injection, but only injection of
one single atom each time.

that is correct. what you are asking for is a very tricky thing to get
right with lots of subtle issues.

people either use a finite reservoir or periodic boundaries in their
simulations.

axel.

Fix append/atoms does "bulk injection": http://lammps.sandia.gov/doc/fix_append_atoms.html . Still, lots of subtle issues remain.

Oleg

Fix append/atoms does "bulk injection": http://lammps.sandia.gov/doc/fix_append_atoms.html . Still, lots of subtle issues remain.

and fix append/atoms is pretty much limited to atomic solids. that is
why i didn't care to mention it.

Yep, good to hear from your confirmation. I also noticed that the usage of “fix append/atoms” is quite limited by its design. So, while the injection could probably be realized by a finite reservoir, does it also infer that the free outlet could be modeled by attaching the exit of the channel to an empty box?

If someone wants to write a new fix that inserts atoms

in some more general way, please have at it.

Fix pour, fix deposit, fix append/atoms are all

reasonable starting points.

Steve