Getting error while using lj/cut/coul/long for the simulation of polymers

I am trying to simulate 4 chains of polymers using LAMMPS. I get an error while using pair_style lj/cut/coul/long but the simulation is running smoothly using lj/cut. I don’t understand that why I am getting an error. Can any one explain me?
Thank you in advance.


You are providing no information about what the error message is or what your input looks like and what your LAMMPS version is or what platform you are running on. One would have to be a mind reader to provide an explanation.

ERROR on proc 1: Bond atoms 700 701 missing on proc 1 at step 95756 (…/ntopo_bond_all.cpp:60)
application called MPI_Abort(MPI_COMM_WORLD, 1) - process 1

LAMMPS = 3 Aug 2022

Here is my input file

Defining the system

units metal
boundary p p p
atom_style full
neighbor 2.0 bin
neigh_modify delay 0 every 1 check yes
bond_style harmonic
angle_style harmonic
dihedral_style opls
improper_style cvff
pair_style lj/cut/coul/long 12.0
read_restart restart_peg_100.min.12000
#read_data “/home/lammps/lammps_peg100.dat”
kspace_style pppm 1.0e-6
write_restart restart_298K_peo100.npt
velocity all create 298.0 30247
dump Dump all custom 1000 “traj_npt_298K_peg100.lammpstrj” id type x y z ix iy iz vx vy vz
thermo_style custom step time cpu pe ke etotal enthalpy temp press vol density cella cellb cellc cellalpha cellbeta cellgamma
thermo 100
fix ensemble1 all npt temp 298.0 298.0 0.1 aniso 1.0 1.0 1.0
timestep 0.002
restart 100000 restart_298K_peg100.npt
run 500000
unfix ensemble1

Thanks for the additional information. This is still not easy to tell what is wrong. By switching from lj/cut to lj/cut/coul/long you are changing the interactions, assuming that your model now also assigns charges to atoms. Those interactions may be stronger, since the Coulomb interaction can be quite strong and specifically does not decay as quickly as Lennard-Jones.

As a consequence, atoms may move faster or get closer (in case the Lennard-Jones interaction is not strong enough to prevent atoms with opposite charge to come very close) and then experience stronger forces. This means the underlying cause of the error is either a too large choice of timestep or an oversight or error with the force field parameters. Which of those applies is difficult to say from remote. I suggest you get some local help from somebody with experience in simulations.

Two additional points:
_ it seems that you are not taking the time to gently bring your system to equilibrium, and go straight to anisotropic NPT with a timestep 2 fs, this sometimes is too brutal. Certain systems require intermediate steps,
_ make sure that your system is charge neutral,

Thank you so much. Now it is working.