Energy Increases too much after minmization

Hello,

I was trying to simulate a PLA molecule and was minimizing it at first. I took a very less velocity (close to zero in the beginning) and the energy of the system increased drastically during the minmization. Timestep of 0.1 was taken and fix nve/limit 0.05 was used. The following output :

Step Temp E_pair E_mol TotEng Press
0 3 -7870.5683 2849.342 -5005.112 -1790.1622
56 3 -1.036369e+17 637.11802 -1.036369e+17 -6.576863e+15

I also tried equilibrating the system with fix nve for same timestep and it just seemed to work fine (even at high temperatures).

What can be the reason that the energy is increasing this much? I have used the correct force field parameters.

units real
boundary p p p
atom_style full
bond_style harmonic
angle_style harmonic
dihedral_style opls
pair_style lj/cut/coul/long 15.0
pair_modify mix geometric
kspace_style pppm 1.0e-4

read_data “datadata.in”
.

.

neigh_modify every 1 delay 0 check yes

velocity all create 3.0 57144
timestep 0.1
fix 1 all nve/limit 0.05
thermo 100
minimize 1.0e-8 1.0e-10 100000 1000000

I don’t see the problem here. Can anyone suggest what mistake from my side makes lammps give this high energy?

Hello,

I was trying to simulate a PLA molecule and was minimizing it at first. I
took a very less velocity (close to zero in the beginning) and the energy
of the system increased drastically during the minmization. Timestep of 0.1
was taken and fix nve/limit 0.05 was used. The following output :

​minimization doesn't use time integration.

Step Temp E_pair E_mol TotEng Press
       0 3 -7870.5683 2849.342 -5005.112 -1790.1622
      56 3 -1.036369e+17 637.11802 -1.036369e+17
-6.576863e+15

I also tried *equilibrating* the system with fix nve for same timestep
and it just seemed to work fine (even at high temperatures).

What can be the reason that the energy is increasing this much? I have
used the correct force field parameters.

​impossible to say without actually being able to reproduce it and knowing
which version of LAMMPS you are using, how it was compiled​ and run.

axel.