Dear LAMMPS user

I am trying to follow one journal where potential is complicated to me. I have written my way. Still, it needs several improvements. Can anyone help me with it? Any kind of suggestion would be helpful for me.

echo both

units metal # set ‘metal’ units (Angstrom,ps timescale)

dimension 3

boundary p p p # periodic BCs

atom_style charge

neighbor 2.0 bin

neigh_modify delay 0 every 1 check yes # neighbor command modifies potential’s natural cutoff_needed?

# ----------------------- ATOM DEFINITION ----------------------------

read_data Fe_Fe3O4_center.lmp

write_dump all atom sinusoid_4.lammpstrj

# --------------- Creat Atoms / Geometry -----------------------

mass 1 55.847

mass 2 15.999

region rPKA sphere 52.127 52.127 104.255 .1 # Create spherical region ‘rpka’ at x, y, x with radius

# ------------------Define Interatomic Potential -----------------

pair_style hybrid/overlay zbl 0.5 7.4 eam/fs morse 2.5 buck 2.5 coul/dsf 0.15 15

pair_coeff 1 1 zbl 26.0 26.0

pair_coeff 1 2 zbl 26.0 8.0

pair_coeff 2 2 zbl 8.0 8.0

pair_coeff * * eam/fs Fe_2.eam.fs Fe Fe

pair_coeff 1 2 morse 0.3 2.0 2.5

pair_coeff 2 2 buck 22764.3 0.1490 20.4

pair_coeff * * coul/dsf

Below, I have given the potential form and table for pair coefficient.

All the interactions between different types of atoms are described using interatomic potentials. All potentials are splined to the ZBL screened Coulomb potential, for close particle separation, using a sixth order exponential polynomial. They are then smoothly truncated to zero at a distance rcut-off. The form of the pair potentials used is given in the following equation :

where rij is the atomic separation, C0–C5 are splining constants, VPot. and VDamp.func. are interatomic potentials and smooth damping functions respectively. The distances ra, rb, rcut, rcut-off are the active ranges for the given expressions. All these values depend on the types of interacting atoms. Values for the constants are given in Table 1. Splining constants were chosen to give a smooth join between VZBL and the sum of VPot. and the Coulomb energy by making V(rij) and its first two derivatives continuous.