[lammps-users] fix wall/reflect question

Dear LAMMPS users,
I would like to have reflective walls in my simulations, but my system requires that the walls do not coincide with the domain boundaries. Is this possible? Or is there a work-around for this type of thing? Thank you very much!

Jonathan

Not currently possible with fix wall/reflect, but it is possible
with all the "soft" walls like fix wall/lj93. I'm not clear
on what your model is, or why you would want to reflect
someplace other than the box boundary. Reflecting
walls are for non-periodic dimensions. So you can always
start your box at the size that puts the wall where
you want, then it doesn't matter if particles move away
from the wall after that.

Steve

Thanks Steve. Actually I need to place charge carriers on the other side of the reflecting walls. I’ve tried explicitly modeling the wall, and want to see if a wall with no interaction energy would help alleviate another problem I am having. Thanks anyway.

Jonathan

I just posted (31May10) a patch than enhances fix wall/reflect to
allow you to put the wall(s) anywhere and make them time varying
via a variable. See if it does what you want.

Steve

Awesome, thanks!

Jonathan

Hi Steve,
With the new fix wall/reflect, is it still necessary that the box be periodic? Thanks.

Jonathan

Oops, the wall must be non-periodic. Nevermind. =)

Jonathan

Hi Steve,
The “EDGE” functionality of the new fix wall/reflect doesn’t seem to be working for me. When I specify the location explicitly, it works, but when I use EDGE it crashes (in about 10 timesteps) and reports missing atoms. When I visualize it, it looks like the box is folded in on itself in each timestep. By the 3rd step, everything has disappeared. Any ideas? Thanks!

Jonathan

Just posted a patch that probably fixes this - 21Jun10 -
please try it out.

Steve

Hi Steve,
Sorry for the delay. It seems to work just fine for me now. Thanks!

Jonathan