Dear all,

I want to produce strongly coupled electron-ion plasma. I am using pair_style Coulomb/long, at low temperature or high coupling (e^2/(4*pi*epsilon_0*Kb*a*T)) because of attractive electron-ion Coulombic potential particle collapses. For removing collapse i want to introduce a interaction potential of type given as

(e^2/(4*pi*epsilon_0*r))*(1- exp(- r/lemda))

where lemda is de Broglie wave length. It is combination of Coulomb and Yukawa. How i produce such type of pair_style in LAMMPS.

Plese help regarding production of this pair_style. My script is given below-

#3D box simulation

# Parameters and constants

variable lu equal 1e-7

variable Q1 equal 1.6e-19

variable Q2 equal -1.6e-19

variable ctf equal 5*{lu}
variable inner equal 0.01*{lu}

variable outer equal {ctf}
variable dtsp equal 1e-15
variable V equal vol
variable T equal 140
variable b equal 3*{lu}

#Initialization

units si

atom_style charge

newton on

dimension 3

boundary p p p

#Atom definition

lattice bcc ${lu}

region simbox block 0 10 0 10 0 10 units lattice

create_box 2 simbox

create_atoms 2 region simbox basis 1 1 basis 2 2

# assume type 1 is positive

group cp type 1

group cn type 2

set group cp charge {Q1}
set group cn charge {Q2}

# Force field

pair_style coul/long ${ctf}

pair_coeff * *

kspace_style ewald 1.0e-10

pair_modify table 0

dielectric 1.0

#Settings

neighbor ${b} bin

neigh_modify every 1 delay 0 check yes one 10000 page 100000

mass 1 1.6708e-27

mass 2 9.1e-31

# temperature controller

compute new3d all temp

# equilibrate

# At 140 K

velocity all create {T} 5812775 temp new3d units box
fix eq1 all nvt temp {T} ${T} 1e-13

thermo_style custom step temp ecoul ke etotal

thermo 200

dump 1 all atom 200 yes.dump

pair_write 1 2 20000 rsq {inner} {outer} table.txt coul_long_Q1_Q2 {Q1} {Q2}

timestep ${dtsp}

run 20000

Thanks & Regards

SANDEEP KUMAR

INSTITUTE FOR PLASMA RESEARCH

GANDHINAGAR, GUJARAT (INDIA), 382428