# To test the "spherical" dihedral_style, we use a coarse-grained n-butane-like
# molecule consiting of only 4 carbon atoms in a chain (hydrogen atoms omitted).
# This molecule contains only one dihedral angle.
# (Unimportant detail: Other interactions use the TraPPE potential 
#  as described in: J Phys Chem B, 1998, volume 102, pp.2569-2577.)

# --- Initialization section ---

units           real
atom_style      full
boundary        p p p
bond_style      harmonic
angle_style     harmonic
dihedral_style  opls
improper_style  none
kspace_style    none
pair_style     lj/cut 15.0
special_bonds  lj 0.0 0.0 0.0

# --- Atom definition section ---

read_data      4atoms.data

# --- Force field parameters ---

pair_coeff 1 1 0.10  1.0
bond_coeff  1  10.0  1.0
angle_coeff 1  10.0  120
dihedral_coeff 1 1.411036 -0.271016 3.145034 0.0

# --- Run time settings ---

timestep        0.125

thermo          1000  # time interval for printing out "thermo" data
thermo_style    custom step pe etotal epair ebond eangle edihed


dump            1 all custom 200 traj_nvt.lammpstrj id mol type x y z ix iy iz

fix            2 all nve

#                        Tstart    Tstop    tdamp     randomseed
fix fxlan all langevin   0.0100    0.0000   1000.0     123456

# (comment out the line above if you want to test energy conservation)



run             0