Hybrid potentials for water moleciules

LAMMPS LAMMPS Beginners
1

I am trying possibility of inserting water molecules into my cutting system.

Dear all,
I need help regarding hybrid potentials and pair coeffs of tip4p and my cutting system. I used explicit Tip4p model in lammps to generate water molecules and inserted my cutting system in it(Attached picture). I defined the type and potentials as follows:

in.Si_C

dimension 3
units metal
newton on
boundary m m p
atom_style atomic
atom_modify map yes
read_data data.water_Si_C_lammpsModel_3_5nm_DoC_3nm_Dis_1nm
mass 1 12.011000
mass 2 28.000000
mass 3 12.011000
mass 4 12.011000
mass 5 28.000000
mass 6 28.000000
mass 7 15.9994 # O
mass 8 1.00794 # H
mass 9 0.01 # X
pair_style hybrid/overlay tersoff lj/cut/tip4p/cut 7 8 0.15 12.0 ##### lj/cut/coul/long/tip4p
pair_coeff * * 2005_SiC_II.tersoff C Si C C Si Si NULL NULL NULL
#################################
pair_coeff 7 7 0.0067 3.1536 ### 0.15 kcal/mol was converted to eV to have 0.0067
pair_coeff 8 8 0.0 1.0
pair_coeff 9 9 0.0 1.0
pair_coeff 7 8 0.0 1.0
pair_coeff 7 9 0.0 1.0
pair_coeff 8 9 0.0 1.0
###################
group boundaryw type 6
group thermostatw type 5
group newtonianw type 2
group newtoniant type 1
group thermostatt type 4
group boundaryt type 3
group water type 7 8 9

#########################
I got this error message:

pair_style hybrid/overlay tersoff lj/cut/tip4p/cut 7 8 0.15 12.0 ##### lj/cut/coul/long/tip4p
ERROR: Illegal pair_style command (src/MOLECULE/pair_lj_cut_tip4p_cut.cpp:427)
Last command: pair_style hybrid/overlay tersoff lj/cut/tip4p/cut 7 8 0.15 12.0 ##### lj/cut/coul/long/tip4p

Water_Model

2

…and deservedly so. Your list of arguments is incomplete for the lj/cut/tip4p/cut substyle.
According to the documentation, there should be 4(!) integers and (at least) 2 floating-point numbers.

Please also note that for the use case you describe, hybrid/overlay seems like the wrong choice since it adds the contribution of different pair styles. You would rather use plain “hybrid” to avoid accidental double counting of interactions.

Please also note that your pair_coeff commands are of incorrect syntax when used with a hybrid pair style and, finally, there are pair_coeff commands missing for then interaction between the water and the atoms modeled with tersoff. LAMMPS cannot generate those automatically.