Dear all lammps users
I’m doing simulation with TIP4P water, OPLS-UA methane, and 3-site hydrogen molecules.
The 3-site hydrogen model I’m using is from J. Chem. Phys. 123, 024507 (2005), which have massless atom at the center of hydrogen molecule with charges -0.9864e.
From paper, they used rigid hydrogen models. Also from searching, i found that lammps cannot support zero mass atom.
So I added fix rigid command to hydrogen molecules with center mass = 1e-10 and -0.9864e charge.
But simulation have some errors, so I found that hydrogen molecules move so fast and system explode.
There is no atom overlapping, I had seriously checked my .dat files. So maybe I think there is a problem with pair or bond interaction.
Also I’ve tried fix rigid/npt, but there is some errors as well.
I just add my input, and data files.
If you guys can give me some advices, I would very appreciate that.
Thank you
Dong woo Kang
<<in.test>>
Initial section
units real
dimension 3
boundary p p p
atom_style full
pair_style lj/cut/tip4p/long 5 4 1 1 0.1250 10
kspace_style pppm/tip4p 1.0e-4
bond_style harmonic
angle_style harmonic
#Atom definition section
read_data test.dat
#Setting section
pair_coeff 1 1 0.294 3.73
pair_coeff 1 2 0 0
pair_coeff 1 3 0.141564001 3.366264993
pair_coeff 1 4 0 0
pair_coeff 1 5 0.248971806 3.43688289
pair_coeff 2 2 0 0
pair_coeff 2 3 0 0
pair_coeff 2 4 0 0
pair_coeff 2 5 0 0
pair_coeff 3 3 0.068164511 3.038
pair_coeff 3 4 0 0
pair_coeff 3 5 0.119882466 3.101731516
pair_coeff 4 4 0 0
pair_coeff 4 5 0 0
pair_coeff 5 5 0.21084 3.1668
group Water type 4 5
group hydro type 2 3
fix 1 Water shake 0.0001 100 0 a 1 b 1
fix 2 hydro rigid/small molecule
thermo 1
thermo_style custom step time etotal ke temp pe ebond ecoul elong press density vol lx ly lz
dump 1 all custom 1 trajectory.lammpstrj.* id mol mass element x y z vx vy vz fx fy fz q
dump_modify 1 element M H1 MSH H2 O
neigh_modify delay 0 every 1 check yes
fix 3 all npt temp 220.0 220.0 100 iso 500 500 100
timestep 1
run 50000000
<<test.dat>>
1746 atoms
1042 bonds
521 angles
5 atom types
2 bond types
2 angle types
20 70 xlo xhi
-10 35 ylo yhi
-10 35 zlo zhi
Masses
1 16.042
2 1.008
3 0.0000000001
4 1.008
5 15.999
Bond Coeffs
1 517.6 0.95719
2 500 0.7414
Angle Coeffs
1 37.95 104.52
2 40 180