Hi lammps users,
I am currently trying to model a system of solvent under external electric field. I am using OPLS-AA force field and NVT ensemble. The system is 100 methanol molecules and the simulation box is cubic with box length as 18.87 angstrom. However when I use 0.1 V/angstrom electric field, the simulation box expands dramatically and obviously it destroys the constant-volume limitation. So could anyone kindly help me check the input file? Many thanks!
The following is my input, and my data file is also attached.
units real
boundary p p p
neighbor 2.0 bin
neigh_modify every 1 delay 0 check yes
atom_style full
bond_style harmonic
angle_style harmonic
dihedral_style opls
improper_style cvff
pair_style hybrid lj/cut/coul/long 12 12
pair_modify mix geometric
kspace_style pppm 1e-5
special_bonds lj/coul 0.0 0.0 0.5
read_data data.lmp
pair_coeff 1 1 lj/cut/coul/long 0.030000 2.500000 # H00 H00
pair_coeff 2 2 lj/cut/coul/long 0.065999 3.500000 # C01 C01
pair_coeff 3 3 lj/cut/coul/long 0.030000 2.500000 # H02 H02
pair_coeff 4 4 lj/cut/coul/long 0.030000 2.500000 # H03 H03
pair_coeff 5 5 lj/cut/coul/long 0.170000 3.120000 # O04 O04
pair_coeff 6 6 lj/cut/coul/long 0.000000 0.000000 # H05 H05
fix SHAKE all shake 0.0001 20 0 b 1 2 3 5
velocity all create 298 298 dist gaussian
thermo_style custom step cpu etotal ke pe evdwl ecoul elong temp press vol density
thermo 1000
fix 1 all nvt temp 298 298 100 tchain 3 mtk yes
fix 2 all deform 1 x final 0.0 18.87 y final 0.0 18.87 z final 0.0 18.87 units box
run 10000
unfix 1
unfix 2
timestep 1
fix 8 all nvt temp 298 298 200 tchain 3 mtk yes
fix kick all efield 0.10 0.0 0.0
restart 10000 MeOH-NVT-E1.restart1 MeOH-NVT-E1.restart2
dump d1 all custom 10000 traj-MeOH-NVT-E1.lmp element xu yu zu
dump_modify d1 element H C H H O H
dump_modify d1 sort id
run 10000000
undump d1
unfix 8
data.lmp (125 KB)