Issues Related with Neighbor bins

Dear LAMMPS users,

During the simulation of pouring particles in a box, I have faced a problem regarding neighbor bins. The error showed in the windows cmd is: “Cannot use neighbor bins - box size << cutoff”. One of the atoms has a diameter 1000 times larger than the smaller ones. I have included some portion of the code in the email. Any kind of help or suggestion is appreciated.

#2D powder pouring in the box

dimension 2

lattice hex 0.88

atom_style sphere #Spheres has per-particle diameter and mass
boundary f fm p
newton off #Two interacting atoms are on different processors and the resulting force information is not communicated.
comm_modify mode multi vel yes #Conserving properties to two ghost atoms

fix prop all property/atom mol ghost yes

region reg block 0 10000 0 5000 -0.5 0.5 units box
create_box 1 reg

create_atoms 1 single 600 2000 0

region substratefirst block 1 6000 1 1000 -0.5 0.5 units box
region substratesecond block 6001 8000 1 1000 -0.5 0.5 units box
region substratethird block 8001 9999 1 1000 -0.5 0.5 units box

region substrate union 3 substratefirst substratesecond substratethird

create_atoms 1 region substrate

group 1 id < 2
group 2 id > 2

set atom 1 diameter 1000

set atom 1 density/disc 500

velocity 1 set 25 0 0 units box

neighbor 0.2 multi
neigh_modify delay 0

Best regards,
Yeasir Mohammad Akib
MS Student

It was resolved by defining the neighbor style to “nsq” but it increases the computation time.

This demo input deck can run with the 27 May 2021 version using the revised multi-cutoff neighbor list code. Only the comm_modify command has to be moved to follow the neighbor command, since those multi-cutoff categories are now linked.