[lammps-users] fix rigid with Granular type

Dear LAMMPS users,

I can not understand quit well how this fix should work on granular type
atoms.

I've defined three granular particles overlaped:

create_atoms 1 single 15.0 15 24.9 units box
create_atoms 1 single 15.5 15 24.6 units box
create_atoms 1 single 16.0 15 24.3 units box

They are fixed rigid:

group clump type 1
fix 1 clump rigid single

and with gravity acting upon them.

Then if I do not exclude their interaction, then they fall, and when
they hit the bottom wall, they rebound, but without experiencing any
rotation. Even more, when they never stop because as the three stands
inclined, the friction makes them move as it some force push them

This strange behaviour disappears if excluding their interaction with

neigh_modify exclude type 1 1

Then when they hit the bottom, they rebound, rotating till they stop
flat.

As far as I can see in the documentation, the behaviour should be the
same, but the performance is affected if the interactions have to be
calculated.

Thanks in advance, best regards.

The script is:

dimension 3
atom_style granular
boundary f f f
newton off

region dominio block 0 30 0 30 0 30 units box
create_box 1 dominio

create_atoms 1 single 15.0 15 24.9 units box
create_atoms 1 single 15.5 15 24.6 units box
create_atoms 1 single 16.0 15 24.3 units box
group clump type 1
fix 1 clump rigid single
#neigh_modify exclude type 1 1

neighbor 1 bin
neigh_modify delay 0

pair_style gran/hertz/history 200000.0 NULL 1000.0 NULL 0.7813 1
pair_coeff * *
communicate single vel yes
timestep 0.0001

fix 2 all nve/sphere
fix 3 all gravity 1.0 vector 0.0 0.0 -1.0
fix zwalls all wall/gran 200000.0 NULL 1000.0 NULL 0.5 1 zplane 0 30
fix xwalls all wall/gran 200000.0 NULL 1000.0 NULL 0.5 1 xplane 0 30
fix ywalls all wall/gran 200000.0 NULL 1000.0 NULL 0.5 1 yplane 0 30
#region slab block 1.0 29.0 1.0 9.0 18.0 21.0 units box

compute 1 all erotate/sphere
thermo_style custom step atoms ke c_1 vol
thermo 1000
thermo_modify lost ignore norm no
compute_modify thermo_temp dynamic yes

run 1 #So pizza do not fail 1
dump mydmp all custom 1000 dump.init id type x y z ix iy iz vx vy vz
fx fy fz omegax omegay omegaz radius
run 300000

Since you are integrating them with fix rigid, why
are you also integrating them with fix nve/sphere?

Steve

2009/12/7 Diego Peinado Martín <[email protected]>: