[lammps-users] two kinds of period in a system with wall

Dear steve and all,

Thanks for your suggestion.

I’ve tried my wall setting and met a unexpected problem. In my system the wall is made of lots of paritcles.

In a system with wall ( z-axis cylinder), the particles inside will be controlled with NPT. Then the box size in z direction will change even the x and y axis are kept as constant. Then the z period of particles inside will different with the wall. If we use the ” dilate partial” in “fix npt” the wall will be just a part in the new enlarged box, and then the particle inside will flow out.

fix npt GB npt/asphere 1.9 1.9 0.1 aniso NULL NULL NULL NULL 1.3 1.3 20 dilate partial

On the contrary, we let the wall scaled with the particle inside under NPT simulation. Then with the box enlarge, the wall will be too dilute to hold all inside particle.

So maybe we need to set two kinds of period. One for the wall, the other for the particle inside. Is it practicable? How can I realize it in Lammps. Or there are some other methods to solve the wall problem? I’ve tried to build longer wall in z axis but failed because when the particle is out of box size it can not be created.

If your system is expanding so much the wall becomes dilute and particles
pass thru, you probably need to make the wall denser.

Steve

2008/2/11 Kitty Ji <[email protected]>: