Hello,
I am try to run md on a polymer system with five PVA chains which contains 50 repeat units and some, say 5, PMDS，trying to mimic the reaction of the system. But now I am stuck on thermostatting the system.
I have tried using velocity command combine with "fix nvt"command. When the run start the temperature arrive at the expected one immediately and the run continues to find that the temperature exploded. My scripts related to thermostatting the system is as follows, companied with the outputs.
Scripts:
atom_style charge
boundary p p p
read_data data.sys
pair_style reax 10.0 1.0e-6
pair_coeff * * ffield.reax 2 1 1 3 2 1 4 3
neighbor 2.0 multi
neigh_modify every 5 delay 0 check yes
restart 10 sio.*.md #dump out the restart file every 10 timestep
thermo 10
thermo_style custom step etotal ke temp pe ebond eangle edihed eimp evdwl ecoul elong press enthalpy etail vol
thermo_modify flush yes
timestep 0.25
dump 1 all xtc 10 min.xtc
dump 2 all atom 10 min.reax..atom
dump 3 all xyz 10 min.reax..xyz
dump 4 all dcd 10 min.reax.dcd
dump_modify 2 scale no
dump_modify 4 unwrap yes
dump_modify 1 precision 10000
velocity all create 298 1234567 dist gaussian
fix 1 all reax/bonds 10 minbonds.tatb
fix 2 all nvt 298 300 2
run 1000
Outputs:
LAMMPS (15 Jan 2010)
Reading data file …
orthogonal box = (0 0 0) to (62.5611 62.5611 62.5611)
1 by 1 by 1 processor grid
7032 atoms
Setting up run …
Memory usage per processor = 27.8556 Mbytes
Step TotEng KinEng Temp PotEng E_bond E_angle E_dihed E_impro E_vdwl E_coul E_long Press Enthalpy E_tail Volume
0 -14024807 6245.5065 298 -14031052 0 0 0 0 -661258.89 -13369794 0 -1187058.6 -18263785 0 244857.34
10 -14945800 16927705 807693.68 -31873505 0 0 0 0 204133.78 -32077638 0 2094483.4 -7466413.7 0 244857.34
STOP Too many torsion angles
By the way, I choose the reax force field to run my MD, And the reax force field file has been modify according to the paper related to thermal degradation of PDMS. Are there any commands I should add to the script, or something else I have take it along in a bad way. Any advices will be welcome.
Thank you in advance!
Best Wishes!
—send by shuping Huang