problem with prism command


I have some problems in using prism command. My lattices style is FCC.How can I build a smooth triangle roughness for wall channels.
I know that I shouldn’t use little size for the width and height of triangle, but I can’t make a good triangle-like corrugation.
every time I plan to change the xy, xz, yz, its shape won’t be like a triangle!!

my geometry part in code is as follows:

lattice fcc 2.35

region box block 0 60.0 0 30.0 0 10.0 units box

region 1 block INF INF INF 1.25 0.0 10.0 units box

group lower region 1

region 2 block INF INF 28.6 INF 0.0 10.0 units box

group upper region 2

region 3 prism 6 12 1.4 5.4 0.0 15.0 2.5 0 0 units box
group rough1 region 3
region 4 prism 12 18 1.4 5.4 0.0 15.0 -2.0 0 0 units box
group rough2 region 4

Also How can I build half of a triangle.

Would you please help me?

Thanks a lot.

The region prism command simply specifies a prism-shaped region,
i.e. in 2d, a rhombus instead of a rectangle. I don't see that
it has anything to do with triangles and rough walls.
LAMMPS does have an atom style called tri, which can be used
to build irregular-shape particles or walls. You can use it
with pair_style tri/cut.