Granular simulation-suggestions

Hi all,

I am trying to do a 2D granular simulation where I try to tightly pack some spherical particles in a box by applying some pressure. Even after this tight packing, I want to apply further pressure and derive a stress-strain relationship. Due to some reason, I am able to witness only small deformations in VMD even though my output file shows otherwise. Also, I tried to compute pressure but my output file does not return such a value. Any suggestions are welcome.
Here is a sample code.


units si
boundary f f p
atom_style sphere
dimension 2
newton off off
communicate single vel yes

Atom Definition

region openbox block 0 0.01 0 0.01 0 14e-6 units box
create_box 1 openbox
create_atoms 1 random 500 3 openbox units box
set region openbox diameter 14e-6 density 1700

neighbor 15e-5 bin
#neighbour modify
pair_style gran/hertz/history 146520146520 180995475113 5e-5 0 0.5 0
pair_coeff * *
timestep 0.000000000005
run_style verlet
fix 2 all wall/gran 146520146520 180995475113 5e-5 0 0.5 0 yplane 0 0.01
fix 3 all nve/limit 6e-6
fix 4 all momentum 1 angular
fix force all indent 3 plane y 0.05 lo units box
compute new all temp
compute 1 all pressure new
dump 1 all xyz 5
run 30000

If anyone can suggest where to find sample granular simulations, that would be great.


Check out LIGGGHTS.
That is a branch of LAMMPS with improved support for granular simulations

Vmd is probably not a good choice since it expects coordinates to be in angstrom, so there can't be a lot of movement when you use si units.