The atoms number in Langevin thermal conductivity calculation

I’m new to Lammps, and try to understand everything in the Langevin example script in thermal conductivity.In the thermal conductivity calculation. The example mentioned that the atoms number of the system is 8000, I think the atoms number is defined by some parameters (fcc$rho, mass, box size), unfortunately, I can’t figure it out. Why is the atoms number 8000 in the system? Can anyone tell me about it? Any help would be appreciated!

Here is the part of Langevin example input:

sample LAMMPS input script for thermal conductivity of liquid LJ

thermostatting 2 regions via fix Langevin


variable x equal 10
variable y equal 10
variable z equal 20

variable rho equal 0.6
variable     t equal 1.35
variable rc equal 2.5
variable     tlo equal 1.0
variable     thi equal 1.70

#variable rho equal 0.85
#variable     t equal 0.7
#variable rc equal 3.0
#variable     tlo equal 0.3
#variable     thi equal 1.0

setup problem

units lj
atom_style atomic

lattice fcc ${rho}
region box block 0 $x 0 $y 0 $z
create_box 1 box
create_atoms 1 box
mass 1 1.0

velocity all create $t 87287

pair_style lj/cut ${rc}
pair_coeff 1 1 1.0 1.0

neighbor 0.3 bin
neigh_modify delay 0 every 1

please take the LAMMPS manual and read the documentation for the individual commands. in your case, particularly read about “lattice”, “region”, “create_box”, “create_atoms”