Temperature and Energy increases with langevin thermostat

Hi Axel,

  Many thanks for your kind reply. I am modeling the Nitrogen as rigid
molecule (it has a massless particle). My LJ coefficients are :

dimension 3
units real
boundary p p p

kspace_style pppm 1.0e-4
kspace_modify order 3
atom_style full
pair_style lj/cut/coul/long 10.0 12.0
bond_style harmonic
angle_style harmonic
pair_modify mix arithmetic

read_data lammps_data.dat

pair_coeff * * 0.0 0.0
pair_coeff 1 8 6.307E-02 3.335
pair_coeff 2 8 0.00 1.655
pair_coeff 3 8 8.59E-02 3.53
pair_coeff 4 8 0.00 1.655
pair_coeff 5 8 0.12255 3.135
pair_coeff 6 8 0.11029 3.155
pair_coeff 7 8 4.629E-02 2.865

pair_coeff 8 8 7.152E-02 3.31

atom type 1 to 7 are fixed with setforce.
atom type (8 and 9) belongs to Nitrogen. atom type 9 is a massless
particle, but it has
  a charge.

The system is unstable when I run the simulation (KE, Fmax and
temperature increases).
  But if I turn off the coulombic interaction, the system is stable.
The force field has been taken from literature (used in GCMC simulations)

thanks for bearing with me,

Surendra

Hi Axel,

  Many thanks for your kind reply. I am modeling the Nitrogen as rigid
molecule (it has a massless particle). My LJ coefficients are :

dimension 3
units real
boundary p p p

kspace_style pppm 1.0e-4
kspace_modify order 3
atom_style full
pair_style lj/cut/coul/long 10.0 12.0
bond_style harmonic
angle_style harmonic
pair_modify mix arithmetic

read_data lammps_data.dat

pair_coeff * * 0.0 0.0
pair_coeff 1 8 6.307E-02 3.335
pair_coeff 2 8 0.00 1.655
pair_coeff 3 8 8.59E-02 3.53
pair_coeff 4 8 0.00 1.655
pair_coeff 5 8 0.12255 3.135
pair_coeff 6 8 0.11029 3.155
pair_coeff 7 8 4.629E-02 2.865

pair_coeff 8 8 7.152E-02 3.31

atom type 1 to 7 are fixed with setforce.
atom type (8 and 9) belongs to Nitrogen. atom type 9 is a massless
particle, but it has
  a charge.

​you keep posting stuff without really making an effort to resolve your
problems and systematically debugging what you are doing.​ i don't have
time to remind you of the same things over and over again. if the
simulation is still not behaving correctly, then the part that is at fault
is still in there.

The system is unstable when I run the simulation (KE, Fmax and
temperature increases).
  But if I turn off the coulombic interaction, the system is stable.

with this ​you are confirming​ yourself, that your force field parameters
are not correct.

The force field has been taken from literature (used in GCMC simulations)

​but obviously not applied correctly. LAMMPS is like any other MD code and
follows the G​I-GO (= garbage in, garbage out) principle.

thanks for bearing with me,

but my patience has reached is maximum extent now. ​this is my last
response on this subject. i am tired of giving advice that is not followed
(or understood?) properly.

axel.