Hi Lammps users,
I’m trying to simulate the reaction between CaO and water using reaxff. My system consists of 384 Ca and O atoms and 32 water molecules. I set timestep as 0.2 fs. When I simulate the system for 1 ns, three water molecules are dissociated and absorbed to the CaO surface. But when I run the same system for 2 ns, only two water molecules are dissociated. So, What would be the reason for this?
I’m referring to this paper, https://pubs.acs.org/doi/abs/10.1021/la204338m. According to that paper, all water molecules should be dissociated within 1 ns. So, How should I improve my input file? Any reply would be much appreciated. My data file and the input file are as follows,
Input
units real
dimension 3
boundary p p p
atom_style full
pair_style reax/c lmp_control safezone 1.6 mincap 100
neighbor 4.0 bin
neigh_modify every 1 delay 0 check yes
----------------- Atom Definition Section -----------------
read_data “system.data”
----------------- force field -------------------------
pair_coeff * * ffield.reax Ca O H O
fix 1 all qeq/reax 1 0.0 10.0 1.0e-6 reax/c
----------------- reaxff energies -------------------------
compute reax all pair reax/c
variable eb equal c_reax[1]
variable ea equal c_reax[2]
variable elp equal c_reax[3]
variable emol equal c_reax[4]
variable ev equal c_reax[5]
variable epen equal c_reax[6]
variable ecoa equal c_reax[7]
variable ehb equal c_reax[8]
variable et equal c_reax[9]
variable eco equal c_reax[10]
variable ew equal c_reax[11]
variable ep equal c_reax[12]
variable efi equal c_reax[13]
variable eqeq equal c_reax[14]
----------------- Minimization -------------------------------
min_style cg
minimize 1.0e-4 1.0e-6 1000 10000
----------------- Equilibration -------------------------------
reset_timestep 0
timestep 0.2
velocity all create 300 12345 mom yes rot yes
fix 2 all nvt temp 300.0 300.0 100
thermo 500
thermo_style custom step lx ly lz press v_eb v_ea v_elp v_emol v_ev v_epen v_ecoa v_ehb v_et v_eco v_ew v_ep v_efi v_eqeq density vol pe ke etotal temp
dump 1 all custom 1000 1traj_nvt.lammpstrj id mol type x y z ix iy iz
run 250000 #50 Ps
unfix 2
undump 1
----------------- run -------------------------------
fix 3 all nvt temp 300.0 300.0 150
dump 2 all custom 1000 2traj_nvt.lammpstrj id mol type x y z ix iy iz
run 10000000 # 2 ns
unfix 3
undump 2
Data file
480 atoms
4 atom types
0.0 20 xlo xhi
0.0 20 ylo yhi
0.0 40 zlo zhi
Masses
1 40.078 # Ca
2 15.999 # O
3 1.008 # H
4 15.999 # O
Atoms # full
1 1 1 0.000000 0.666000 0.028000 0.264000
2 1 1 0.000000 0.609000 2.468000 2.682000
3 1 1 0.000000 2.912000 0.033000 2.588000
4 1 1 0.000000 2.922000 2.514000 0.212000
5 1 2 0.000000 3.070000 2.524000 2.720000
6 1 2 0.000000 2.931000 0.110000 0.029000
…