[lammps-users] NVT/NPT error

Dear all,
When I perform NVE or NPT my model is not attain the equilibrium state.It continuously increases the both pressure and temperature.

Here is my input file.


units metal
dimension 2
boundary p p p
atom_style atomic

lattice custom 1.42 a1 3.0 0.0 0.0 a2 0 1.7320 0.0 a3 0.0 0.0 4.718309859 &
basis 0.0 0.0 0.0 basis 0.333 0.0 0.0 basis 0.5 0.5 0.0 basis 0.833 0.5 0.0 basis 0.166666 0.5 0.5 basis 0.3333333333 0.0 0.5 basis 0.6666666666666 0 0.5 basis 0.8333333333333 0.5 0.5

region SimBlock block -10 10 -10 10 -0.25 0.25 units box
region GrapBlock block 0 8.52 0 4.91888 -0.25 0.25 units box
create_box 1 SimBlock
create_atoms 1 region GrapBlock basis 1 1 basis 2 1 basis 3 1 basis 4 1 basis 5 1 basis 6 1 basis 7 1 basis 8 1
mass 1 12.01

pair_style airebo 3.0 1 0
pair_coeff * * …/…/potentials/CH.airebo C
velocity all create 300 13 dist uniform
set region GrapBlock type 1

neighbor 1.0 bin
neighbor_modify delay 20

fix 1 all nvt temp 300.0 300.0 1000.0

dump 1 all atom 1 dump.atom

thermo 20
thermo_style custom step pe ke etotal temp press

timestep 0.001
run 3000

Please can anyone help me to figure it out this error?
Thanks

Best regards,
Buddhika

Dear all,
When I perform NVE or NPT my model is not attain the equilibrium state.It
continuously increases the both pressure and temperature.

have you run any longer? perhaps it is not equilibrated yet?

axel.

yes sir. Even ran up to 100,000 runs .But didn’t come to equilibrium state.

1. Try changing

fix 1 all nvt temp 300.0 300.0 1000.0

to

fix 1 all nvt temp 300.0 300.0 1.0

Your damping parameter is too large. Remember that you are working
with 'metal' units.

2. Try changing

velocity all create 300 13 dist uniform

to

velocity all create 300 13 dist gaussian

Regards,
Zhun-Yong

Dear all,
Thanks for replies.
but still am unable to sort it out.Even I ran the input script for 100000 ,it didn’t come to equilibrium state.Please can anyone explain how can I achieve the equilibrium state at room temperature ?

If I use "fix temp/berendsen " and NVE can I consider this state as a equilibrium state? I guess it is not the real equilibrium state. This command kept the system under certain conditions isn’t it?
best regards,
Buddhika