As a newcomer to LAMMPS, I definitely need your help.
I would like to run a simulation with only two types of pair potentials (no bond, angle,dihedral,etc): Lennard-Jones and Coulomb. As a first approach, I chose the lj/cut/coul/cut pair_style.
My input script contains the following lines.
Is it correct to use the line "atom_style charge" combined with the command "pair_style lj/cut/coul/cut 8.75 20" ?
(This script also calls the file system.dat that defines the masse of the atoms and the atoms via the following line:
1 1 -1 -331.074383386 -331.074383386 -1.32953354535 (Atom-ID, Atom-type, Charge, x, y, z))
pair_style lj/cut/coul/cut 8.75 20
pair_coeff * * 100 3.5 8.75 20
# Define groups
group water 1
group solid_neutral 2
group solid_charged 3
group cations 4
group anions 5
# temp controllers
temperature water_temp water full
temperature cations_temp cations full
temperature anions_temp anions full
temperature solid_neutral_temp solid_neutral full
temperature solid_charged_temp solid_charged full
velocity water create 298.0 887723 temp water_temp
velocity cations create 298.0 887723 temp cations_temp
velocity anions create 298.0 887723 temp anions_temp
velocity solid_neutral create 298.0 887723 temp solid_neutral_temp
velocity solid_charged create 298.0 887723 temp solid_charged_temp
# Fix solid atom around initial position
fix tether solid_neutral spring/self 100
fix tether solid_charged spring/self 100
# Keep solid temperature constant
fix 1 solid_neutral nvt 1.00 1.00 10
fix 2 solid_charged nvt 1.00 1.00 10
fix 3 water nve
fix 4 cations nve
fix 5 anions nve
# Enforce 2d calculation
fix 1 all enforce2d
# Save results every 100 frames (positions and thermodynamics data)
dump 1 all xyz 100 electrokinetics.out
So far it crashes immmdiately. There must be something wrong with the initial position of the atoms or an inproper charge or energy (unit problem). I am looking for the problem but I just would like to know if I am going in the right direction.
I have another question. Most of the atoms are not charged, so the LJ potential is enough. Some atoms are charged, therefore I need to had the Coulombic interaction. But so far all the atoms undergo both potentials. I just put either a zero or non-zero charge whether the atom is interacting with LJ or LJ+Coulomb.
Is it possible to run the LJ potential only on some types of atoms and run both LJ and Coulombic on other types of atoms ?
I thank you ahead for your help and possible answers.
Have a good day.