[lammps-users] thermal conductivity of argon


I am trying to calculate the thermal conductivtiy of argon at 30K using fix/thermal conductvity. Below is the code i used. The NVT part is working fine but when the ensemble is NVE, the temperature of the system is increasing above 100K for some reason which i don’t know. Can you please take a look and let me know if anything is wrong??

units metal
dimension 3
boundary p p p

atom_style atomic

lattice fcc 5.26
region box block 0.0 4.0 0.0 4.0 0.0 16.0
create_box 1 box
create_atoms 1 box

mass 1 39.948

pair_style lj/cut 2.5

pair_coeff * * 0.01032 3.405 2.5

velocity all create 30.0 873586443 dist gaussian
fix 3 all nvt 30.0 30.0 0.2 drag 5.0

timestep 0.0005

run 50000

unfix 3

fix 4 all nve

fix 5 all thermal/conductivity 100 z 20

timestep 0.0005
thermo_style custom step temp pe ke f_5
thermo 100
run 1000000

I don't see anything obviously wrong. That's a pretty tiny system. You
would need to be sure not to perturb it dramatically via the fix thermal/cond.