# Identify the exact number atoms simulation – LAMMPS General Discussion

Hi every one!
I have problem the number of atom is increasing (diamond structure)
for example i have 24 atom(0.1%) for other atom (nitrogen N) after simulation the number of atom becomes more at each step (7362)( 21.7%) be the increase =24 atom I don’t know why the number increased and where did these atoms come from. Can I keep the number of atoms constant? what the command for LAMMPS should be use
lammps-users Digest, Vol 81, Issue 65

If you want helpful answers, you have to write posts that people can make sense of, that properly describe the problem and provide sufficient detail that somebody from remote, who does not know what you are doing and cannot look over your shoulder, can understand what happened and then make a suggestion.

All that can be found out from your post is that you have done some simulation of an unknown system which apparently contains some nitrogen atoms and then did some kind of analysis and the results are not what you expect.

What is extremely confusing is that you say the number of atoms is increasing. That cannot be unless your simulation contains commands that add atoms. Since we don’t know what system you are simulating how and also don’t know what kind of analysis you are doing with what software, there is nothing that can be recommended.

This question makes no sense without context. The number of atoms is an input parameter of a simulation.

There rarely is a case where adding a single (magic) command that can “fix” a problem. However, in this case it is completely unclear what the problem as such is. However, understanding the problem is a prerequisite to figuring out a solution.

What has a digested mailing list message containing 16(!) emails to do with your problem?

units metal
dimension 3
boundary p p p
atom_style atomic
variable t equal 1800.0
atom_modify sort 0 0.0

lattice custom 5.431 a1 1.0 0.0 0.0 a2 0.0 1.0 0.0 a3 0.0 0.0 1.0 basis 0.0 0.0 0.0 basis 0.5 0.5 0.0 basis 0.0 0.5 0.5 basis 0.5 0.0 0.5 basis 0.25 0.25 0.25 basis 0.25 0.75 0.75 basis 0.75 0.25 0.75 basis 0.75 0.75 0.25

region box block 0.0 10.0 0.0 10.0 0.0 10.0

group C type 1
group N type 1

mass 1 12.01115
mass 2 14.0067

pair_style tersoff
pair_coeff * * BNC.tersoff N C C

compute 1 all ptm/atom dcub 6 all
compute peratom all pe/atom
reset_timestep 0

timestep 0.001
velocity all create 300 16666 mom yes rot no
fix 1 all npt temp 300 300 1 iso 0 0 1 drag 1

dump 1 all custom 10 dump.equil.* id type xs ys zs c_peratom fx fy fz

thermo 10
thermo_style custom step lx ly lz press pxx pyy pzz pe temp

run 100
unfix 1

variable tmp equal “lx”
variable L0 equal {tmp}
print “Initial Length, L0:
{L0}”
undump 1
reset_timestep 0
fix 1 all npt temp 300 300 1 y 0 0 1 z 0 0 1 drag 1
variable srate equal 2.0e10
variable srate1 equal “-v_srate / 1.0e12”

variable strain equal “(lx – v_L0)/v_L0”
variable p1 equal “v_strain”
variable p2 equal “-pxx/10000” ## 1ГПа = 10000 бар
variable p3 equal “-pyy/10000”
variable p4 equal “-pzz/10000”

dump 2 all custom 10 dump.deform.* id type xs ys zs c_peratom fx fy fz

thermo 10
thermo_style custom step v_strain temp v_p2 v_p3 v_p4 ke pe press
run 100

print “All done”