Hi all,

I am trying to simulate coarse grained cellulose chain using martini force field parameters.

I used the following parmeters from this Paper (https://pubs.acs.org/doi/10.1021/jp5105938)

```
pair_coeff 1 1 1.33 4.7
pair_coeff 2 2 0.478 6.2
pair_coeff 3 3 1.33 4.7
pair_coeff 4 4 1.33 4.7
pair_coeff 5 5 0.478 6.2
pair_coeff 6 6 1.33 4.7
bond_coeff 1 71.7 2.32
bond_coeff 2 71.7 2.22
bond_coeff 3 71.7 5.55
bond_coeff 4 71.7 2.20
bond_coeff 5 71.7 2.30
angle_coeff 1 11.95 166
angle_coeff 2 11.95 85
angle_coeff 3 11.95 85
angle_coeff 4 11.95 113
angle_coeff 5 11.95 80
angle_coeff 6 11.95 165
dihedral_coeff 1 2.39 1 0
dihedral_coeff 2 2.39 1 0
```

The (.in) file is given below:

```
units real
dimension 3
boundary p p p
atom_style full
# neighbor 2.5 bin
# neigh_modify delay 5
pair_style lj/cut 12.0
#pair_modify mix arithmetic
pair_modify shift yes mix geometric
bond_style harmonic
angle_style harmonic
dihedral_style harmonic
read_data cell5.lmp
include Parameter.lammps
# Assign original velocities to atoms
compute new all temp
velocity all create 298.1 487639 temp new
# Set up ensemble
fix 1 all nvt temp 298.1 298.1 100.0
timestep 5
# Output temperature, energy, pressure of the system
thermo_style custom step temp etotal pe ke pxx pyy pzz
thermo_modify flush yes
thermo 100
dump 1 all xyz 100 dumpcg13.xyz
run 200000
write_data cg13.data
```

But, I am not getting the negative potential energy. Do you have any suugestions?

Thanks,

Pinky