# LAMMPS Input Script for Water Droplet on Anatase Surface

# Initialize simulation
units           real
boundary        p p p
atom_style      full
bond_style      harmonic
angle_style     harmonic
special_bonds lj/coul 0.0 0.0 0.5


# Read anatase data file
read_data       anatase.data extra/atom/types 2 extra/bond/types 1 extra/angle/types 1 extra/bond/per/atom 4 extra/angle/per/atom 4 extra/special/per/atom 4  

# Adjust box size in z-direction
change_box      all z final 0.0 500.0

# Define masses for water atoms (SPC/E model)
mass            3 15.9994  # Oxygen
mass            4 1.008    # Hydrogen

# Load water molecule template
molecule        water spce.mol

# Define liquid region for water placement
region          liquid block 0.0 100.0 0.0 100.0 0.0 100.0

# Create water molecules in the liquid region
create_atoms    0 random 512 23462134 liquid mol water 85342 overlap 1.333


# Define groups
group           H2O type 3 4
group           slab type 1 2


# Constrain SPC/E water molecules
fix myshk H2O shake 1.0e-4 100 10000 b 1 a 1

# Apply constraints to fix the titania slab
fix walls slab setforce 0.0 0.0 0.0

# Bond coefficients for SPC/E water
bond_coeff      1 450.0 1.0   # Bond type 1: Oxygen-Hydrogen bond

# Angle coefficients for SPC/E water
angle_coeff     1 55.0 109.47  # Angle type 1: H-O-H angle

# Define pair interactions
pair_style      hybrid/overlay lj/cut/coul/long 10.0 buck/coul/long 10.0
pair_coeff      * * lj/cut/coul/long 0.0 0.0
pair_coeff      1 3 buck/coul/long 1000.0 0.5 0.0  # TiO2-Oxygen (adjust parameters as needed)
pair_coeff      1 4 buck/coul/long 1000.0 0.5 0.0  # TiO2-Hydrogen (adjust parameters as needed)
pair_coeff      3 3 lj/cut/coul/long 0.1553 3.166  # SPC/E water model (O-O)
pair_coeff      3 4 lj/cut/coul/long 0.0 0.0       # SPC/E water model (O-H)
pair_coeff      4 4 lj/cut/coul/long 0.0 0.0       # SPC/E water model (H-H)


# Long-range electrostatics
kspace_style    pppm 1e-4

# Thermostat for the entire system
fix             mynvt all nvt temp 300.0 300.0 100.0


# Initialize velocities
velocity        all create 300.0 465135

# Output settings
reset_timestep  0
thermo          100
thermo_style    custom step temp press vol density

minimize 1.0e-4 1.0e-6 1000 10000

# Dump trajectory
dump            mydmp all atom 1000 dump.lammpstrj

# Set timestep
timestep        1.0


# Run simulation
run             5000

# Write final data file
write_data      data.anatase_water