prism region

LAMMPS LAMMPS Mailing List Mirror
1

Hi,

i'm trying to define embed a prism region in a simulation but i'm afraid there is something i don't understand well.

Briefly, i have a drop of water and i bound it with a wall below and above in the z-direction. In the wall below, i embed particular regions (in the example below the embedded region is a strip infinite in y and finite in x and z)

This example works:

region 1 block INF -5 INF INF INF -6 units box side out
region 2 block -5 -5 INF INF -6 -2 units box side out
region 3 block -5 5 INF INF INF -2 units box side out
region 4 block 5 5 INF INF -6 -2 units box side out
region 5 block 5 INF INF INF INF -6 units box side out

fix zero all wall/lj126 zhi 200.0 0.03 3.0 12.0 units box pbc yes
fix first all wall/region 1 lj126 0.03 3.0 12.0
fix second all wall/region 2 lj126 0.03 3.0 12.0
fix third all wall/region 3 lj126 0.03 3.0 12.0
fix fourth all wall/region 4 lj126 0.03 3.0 12.0
fix fifth all wall/region 5 lj126 0.03 3.0 12.0

This other, however, which now includes a prism, reports lost atoms

region 1 block INF -5 INF INF INF -6 units box side out
region 2 prism -5 5 INF INF -6 -2 0 0 0 units box side out
region 5 block 5 INF INF INF INF -10 units box side out

fix zero all wall/lj126 zhi 200.0 0.03 3.0 12.0 units box pbc yes
fix first all wall/region 1 lj126 0.03 3.0 12.0
fix second all wall/region 2 lj126 0.03 3.0 12.0
fix fifth all wall/region 5 lj126 0.03 3.0 12.0

I thought both are equivalent but clearly they are not. Not sure why though.

I'm using LAMMPS 11 Sep 2014.

Thanks
Miguel

2

I’m not following all the geometry and what you mean by “embed
regions”, but you should
check the fix wall/region doc page and its notes about
the kinds of regions that cause problems. It could be
than an interior corner of a prism causes a problem.

Steve

3

Steve,

Thanks. I've attached a small picture here that shows, i hope better, what i'm trying to do.

I'm using two options. Option a) works; option b) crashes.

In each case, the regions are "fixed" as wall/region lj126.

If i understand the definition of regions correctly, it seems to me that both options are equivalent.

I had checked before the section of the manual that describes the problems related to convex/concave corners. It could be that option b), which includes a rectangular prism, crashes because of this problem. Yet, if option b) is equivalent to a), then a) should crash as well. But this is not the case.

Thanks
Miguel
[cid:[email protected]...]

regions.jpg