Dear Lammps users/developers,

I’m performing a simulaion on the equilibrium of a cluster which is formed by the condensation of water moleciles (rigid Tip5p) on an acetic acid (nonconstrained) cluster. However, my simulation will go wrong after several steps, although I change of timestep to 0.1 fs.

Following is my “in” file, and the data file is in the attachment.By the way, if I use the spce water model to replace the Tip5p ater model, the simulation is successful.

I cannot find tne reason for this error in the manual. Would you please give me some suggestions?

I would appreciate any help and suggestion.

Thanks so much!

Best regards!

Chao

# 1. Initialization:

processors 2 2 2

units real

boundary p p p

dimension 3

atom_style full

# 2. Atom definition:

read_data 120ch3cooh.lammps05

mass 1 12.011 # C (-H)

mass 2 12.011 # C (-C)

mass 3 15.9994 # O (=O)

mass 4 15.9994 # O (-H)

mass 5 1.008 # H (C-H)

mass 6 1.008 # H (O-H)

mass 7 15.999400

mass 8 1.008

mass 9 1.0e-6

group acetic type 1 2 3 4 5 6

group water type 7 8 9

neighbor 2.0 bin

neigh_modify every 1 delay 0 check yes page 300000 one 5000 exclude molecule water

timestep 1

# 3. Force fields:

pair_style lj/cut/coul/long 14.0

# I J eps(kcal/mol) sigma(A)

pair_coeff 1 1 0.066 3.5 #C(CH)

pair_coeff 1 2 0.0832 3.625

pair_coeff 1 3 0.1177 3.23

pair_coeff 1 4 0.1059 3.25

pair_coeff 1 5 0.0445 3.0

pair_coeff 1 6 0 0

pair_coeff 1 7 0.1027 3.31

pair_coeff 1 8 0 0

pair_coeff 1 9 0 0

pair_coeff 2 2 0.105 3.75 #C(C=O)

pair_coeff 2 3 0.1485 3.355

pair_coeff 2 4 0.1336 3.375

pair_coeff 2 5 0.0561 3.125

pair_coeff 2 6 0 0

pair_coeff 2 7 0.1296 3.435

pair_coeff 2 8 0 0

pair_coeff 2 9 0 0

pair_coeff 3 3 0.21 2.96 #O(=O)

pair_coeff 3 4 0.1889 2.98

pair_coeff 3 5 0.0794 2.73

pair_coeff 3 6 0 0

pair_coeff 3 7 0.1832 3.04

pair_coeff 3 8 0 0

pair_coeff 3 9 0 0

pair_coeff 4 4 0.17 3.0 #O(OH)

pair_coeff 4 5 0.0714 2.75

pair_coeff 4 6 0 0

pair_coeff 4 7 0.1649 3.06

pair_coeff 4 8 0 0

pair_coeff 4 9 0 0

pair_coeff 5 5 0.03 2.5 #H(CH)

pair_coeff 5 6 0 0

pair_coeff 5 7 0.0693 2.81

pair_coeff 5 8 0 0

pair_coeff 5 9 0 0

pair_coeff 6 6 0 0 #H(OH)

pair_coeff 6 7 0 0

pair_coeff 6 8 0 0

pair_coeff 6 9 0 0

pair_coeff 7 7 0.1599 3.12 #O-O

pair_coeff 7 8 0 0

pair_coeff 7 9 0 0

pair_coeff 8 8 0 0 #H-H

pair_coeff 8 9 0 0

pair_coeff 9 9 0 0

bond_style harmonic

# N k/2(kcal/mol/A^2) r0(A)

bond_coeff 1 340 1.09 #c-h

bond_coeff 2 317 1.522 #c-c

bond_coeff 3 570 1.229 #c=o

bond_coeff 4 450 1.364 #c-o

bond_coeff 5 553 0.945 #o-h

angle_style harmonic

# N k/2(kcal/mol/rad^2) theta0(degree) K_UB(en/dis^2) rub(A)

angle_coeff 1 33 107.8 #H-C-H

angle_coeff 2 35 109.5 #H-C-C

angle_coeff 3 80 120.4 #C-C=O

angle_coeff 4 70 108 #C-C-O

angle_coeff 5 80 121 #O=C-O

angle_coeff 6 35 113 #C-O-H

dihedral_style opls

# N K1(kcal/mol) K2 K3 K4

dihedral_coeff 1 0 0 0 0 #H-C-C=O

dihedral_coeff 2 0 0 0 0 #H-C-C-O

dihedral_coeff 3 1.5 5.5 0 0 #C-C-O-H

dihedral_coeff 4 0 5.5 0 0 #O=C-O-H

kspace_style pppm 1.0e-4

variable T equal 100

velocity all create 100 87287 loop all dist gaussian

fix a1 acetic nvt temp $T $T 100

fix b1 water rigid/nvt molecule temp $T $T 100

compute t1 acetic temp

compute t2 water temp

thermo_style custom step temp c_t1 c_t2

thermo 500

dump 1 all custom 5000 dump.meltq401 id type x y z mass q

run 1000000

120ch3cooh.lammps05 (507 KB)